The fact that you are asking these questions shows you have a healthy respect for the dangers of handling Li-ion cells. I think you’ll be fine with any of the lights you mentioned. All you need is some decent cells and a reliable charger.
Stick around and do lots of reading. There’s a wealth of knowledge to pick up from the experienced members here.
I personally have not had good luck with Olight lights, to the point that I won’t buy another. My Javalot has been great, but the 2 batons I had were both glitchy. They never quit on me entirely, but they just weren’t predicable. They both had issues coming on in the right mode and with switching between modes. One of them had onboard charging that did not work consistently.
I don’t think the FW series of lights is for you. The people that got working lights love theirs, but search for any FW thread here and look at the number of people that have huge issues with them. ranging from small glitches to outright dangerous lights.
That said though, anything with a lithium battery can be dangerous if you ignore the precautions you should be taking. They do a good job of making them very safe, but google iPhone fire and you’ll get tons of hits from people with property damage or injury from a phone (iPhone or other) catching on fire. Almost all of them seem to have started though with people not taking proper precautions while charging them.
It’s really like anything else, learn a little bit and take the right precautions and you will be fine. You probably already do it in most areas of your life without realizing.
Think of it like a car. The batteries are like the gas you put in it. 4.2V is a full gas tank, 3.7V (or somewhere around there) is half a tank, and you need to refuel (recharge) when you get down into the lower 3Vs. The current is like the octane rating, higher performance cars need higher octane gas (generally speaking). Brighter lights need batteries that provide more current. And you need to use safety precautions when you refuel. After all, you wouldn’t light a cigarette when you’re filling up your gas tank would you? You already understand all the principles you need to know to use batteries safely.
You know the old saying; “You cannot win, if you do not play.”
Your analysis and writing clearly shows you are smart enough to get a handle on this subject. It may not be your ‘cup of tea’ (everyone has unique strengths and weaknesses), but you surely seem to have enough “on the ball” for basic competence. You’ve done a basic analysis of your problem. Now you need the info and skills to solve the puzzle. They are more basic than you might think.
Start small, work up. That’s what we ALL do.
So…what’s going on with your light? By your description it could be ‘the light’, but my bet is the battery. Fairly easy test, get a new top tier battery and see if that fixes it. All rechargeable batteries die. Yours should have lasted longer than that, but without some appropriate testing, none of us is going to know. THAT’S where some basic knowledge, and a few tools, comes in handy.
First tool, Do you have a digital volt meter? If not, get one. It is probably the most useful basic tool and useful beyond flashlight batteries.
(Note - due to pandemic issues, and commercial battery consumption changes, getting a good battery has become somewhat more difficult. Not impossible though.)
If you care to divulge where in Canada you live, there may be a BLF member who can help you out in person. Much easier and more fun.
Well...I would say...do not despair. Sounds like this is just a matter of defective lights, not your competency or ability to understand - not at all.
I'm not an Olight user and haven't ever tried to keep up with their offerings' characteristics other than (stupid) proprietary battery designs. It's good that they took care of you, twice even, so you're not out any cash, just a little time and frustration. You might search this forum and CPF a little, maybe even youtube, to see if that particular light and time of manufacture is known to have some defects. Sometimes those appear right away and sometimes they just fail over time. If the third one dies, you might ask them if they're willing to replace it with a similar model if the design is likely to fail yet again (assuming there was a design issue and they addressed it...that happens a lot with many manufacturers if they keep the model for sale over time).
Hard to say anything about your light's issue but of course generally flickering indicates an unsteady connection of the electricity somewhere. Very often that can be something as simple as stray grease/oil on threads or battery contacts and cleaning it up fixes everything. Many lights use the connection between tail cap and tube body as a conductor, so having those surfaces clean is smart, too (and the same on the head end). Many lights also use little skinny threaded rings to clamp the driver board into its place and/or the tail spring board into its place. With normal use sometimes those retaining rings will loosen up a little and need to be snugged down again, or perhaps they were never snugged properly at the factory. When they get loose the electrical connection either cuts out or becomes erratic and weird things can happen. So checking these basic things is something easy that you can do and watch out for.
Defective batteries are rare so as long as you're using quality ones you shouldn't see issues there (contacts clean of course). And then that brings us to the nitty gritty of more complex failures, which does take some learning and basic tools to try and diagnose. Drivers seem to fail a lot although some last many many years with constant use and never give any issues at all. But if a solder joint somewhere was poor to begin with, it may fail down the road and cause who-knows-what kind of issues, and sometimes the little chips and components can fail, too. Maybe the stripped end of a wire wasn't done properly or positioned correctly and works for awhile before causing a short in a circuit. These are things that are harder to figure out and understand, but if you want to (or need to) you certainly can. And this forum is fantastic for that.
Other than the basic cleanliness and snug connection stuff, none of this is competency...it's just living with affordable electronic designs. :) When we pay more money, sometimes the designs and parts aren't necessarily any better than less expensive items, but you're often paying for some availability of service after the sale, parts, warranty replacement, etc (and of course....the dreaded Marketing). With some companies you're kind of on your own to figure it out and fix it, but ones like Olight and some others will be there for you. They may not be "budget" pricing but they do have that going for them. And then there are some companies who charge more, promise the service and assistance, and still leave you out in the cold.
CRC… It is really not all that complicated.
Stick with a good brand battery, Panasonic, Samsung, Sony… to name 3.
Pick a flashlight you want & just ask here on the forum what battery to get.
Many will say get a “protected” battery. Personally I NEVER buy “protected” battery anymore.
When I first started in this long ago I wasted a bunch of money on protected batteries.
Live & learn I guess. 
Anyway… choosing a battery is just not that big a deal. IF you don’t know… just ask. 
Have you read the links I gave you above a few days ago CRC??
The one on LiIon battery saftey & then Battery University.
IF you have… what do you not understand about what you read??
You seem to be willing to do extensive research and reading on lights, but don’t appear to have done any reading on the battery links at all.
That’s a bit like reading about and studying new cars, really wanting one, but unwilling to learn to drive….because it’s too hard.
You have been led to the water. Take a drink.
Basically you can think of cells in two groups as far as "matching" one to a light...and really that's not often a huge issue with decent cells.
Low/Standard drain: These cells have magic jelly inside that gives them a higher mAh rating so they store more juice and can give longer run times, apples to apples. The tradeoff is that they can only handle so much heat (current draw) and these days that's usually at least 8 amps or so, and the vast majority of lights are still in the 1.5 to 6 amp range, so these cells are just fine. If you put a standard cell like this into a powerhouse light that pulls 10 amps or whatever, then at a minimum there's going to be so much heat buildup and performance loss that you'll be unhappy...and there may be other issues with the battery itself or the components on the driver, etc, maybe even the springs in the light.
High drain: The magic jelly in these is slightly different and allows them to withstand the heat of much higher currents running through them, but their tradeoff is that they don't store as much, so even with lower currents they have shorter run times. These will generally be at least a 15 amp rating but can be double that or more. We talk about those ratings with their "continuous drain" rating...what they can run at all the time and be happy. They also have a "pulse rating", which is much higher and meant to convey what they can handle for brief bursts, like turbo mode or vaping or a "max" setting on a vacuum, etc. You can put a high drain cell in any normal lower performing light, you'll just have shorter run times.
Then you can have added protection circuits to any of these cells. Generally not necessary - if your light doesn't have any protection built in to the electronics then you just don't pull an oops and leave the thing turned on unattended to where the battery drains alllll the way down. Otherwise you're good. These protection circuits (can be read about and seen in photos in the above links) are tacked on to the standard as-manufactured cell by the companies that sell them. Usually a tiny circuit board on the negative end, a conductor that runs up the side to the positive end, and another cap there...then it's all sealed up in a second plastic shrink wrap on top of the original manufacturer's shrink wrap. Depending on the maker and the cell size/circuit choice, this added protection extends the cell length by 3mm-8mm or so. Sometimes that added length is a problem for some light designs and you have to use plain normal factory cells in those (or explore modding avenues to let longer cells fit). The current drain on protected cells is almost always lower than the factory cells...again, that just depends on things, and these days the current rating for some protected cells is a lot higher than it used to be, which is great if you want protection for whatever reason. They also cost more and you're limited in choices.
So unless you have a high drain light that's really pushing the lumens for the included components, standard cells will often be a fine choice. If your light needs high drain cells, then pick up a couple for the collection. I would stay away from the cells with on-board charging. I've only had a few of them and they're so-so, but all of them had lower mAh and two of them failed (charging circuit...cell was ok). To make room for the charging components you necessarily have to reduce the height of the cell if you want to stay in standard dimensions...thus less magic jelly inside to work with. They can be convenient, though, and in emergency times you can just use some other juice pack to charge them up whereas a normal charger will require electricity (unless it will take a 12v DC car adapter).
So...look at the specs for the light(s) you want and look up reviews here that provide real life testing with numbers. If it turns out your light wants 10 amps then be sure you have a cell that will deliver, and if it's a normal just-a-few-amps light then you're good with whatever.
Excellent CRC, keep it up.
I'm sorry that you got scared, but maybe you'll feel better as time passes.
If you decide to come back sometime, you're always welcome here, CRC. 
(And I don't think that you wasted our time.)
...
Although Li-Ion cells are really liked around here, you could just stick to AA and AAA flashlights.
Be sure to get some Eneloops, and you can still be a flashaholic. 
CRC…. If I may ask, how old are you??
Hey, at least you know how to use the internet and you found BLF.
That takes some brains.
I also have anxiety and depression, and am mentally disabled.
I have very few responsibilities in life, and I like it that way.
Plus, I'm pretty antisocial in real life, so we have some things in common.
Better toss out your cellphone(s), earbugs, mp3 players, everything else that has a Li cell in it, then.
I hope you realize you are freaking out over a possible but pretty rare occurrence? I’ve been using these batteries for a long time, unfortunately dropped many, and have created no disasters.
Statistically the most dangerous place in your life is your house……
Knowing that are you going to move out?
If you like the light, but are now genuinely afraid of lithium batteries, switch over to NiMh. They are generally considered safer, and you can still get some serious light out of them. How much light do you really need if you aren’t prowling the streets or woods after dark.
Note-you’ll find people that will tell you that NiMh have dangers too. Being alive has dangers. You gotta weigh the acceptable and reasonable from the excessive. That decision is always personal.
BTW - I appreciate your candor. I think more of you for opening yourself up, not less.
It was certainly difficult to do so, but it actually helps to know where you are really coming from.
And don't beat yourself up so badly about school or learning...seriously, those aren't indicators of your actual abilities! It's a little harder today maybe without college degrees and such but there are PLENTY of people who start out adult life in the same way(s) and go on to be happy and successful one way or another. Some people don't settle into their groove until they're in their 40s or 50s. And the yardstick by which society tends to measure "success" isn't always very accurate or fair, anyway...that's the truth.
Also...your now-flickering light. I think I said this in another comment here, but that tells you something got knocked out of whack with the impact, so somewhere in there electricity is not getting solid connection. There's no way to say what it is exactly without digging into the nitty gritty and trying to diagnose it. It could be as simple as needing to tighten a retaining ring in the head or tail, or it could be a broken solder joint or some other thing. Most of our lights are not "potted", which is when they cover the electronics and fill up space with rubber goop (which has advantages - like impact protection - and disadvantages), so harsh impacts tend to have consequences beyond just dinging up the aluminum housing...it's a crap shoot after a good drop. Disappointing but nothing to worry about with safety.
Want to learn more about batteries, good brands, how they work, and what NOT to do? Start watching and reading everything Mooch puts out. Ive been a patreon for a bit, best $1 a month i spend. HKJ here on BLF is Awesome too!
18650 battery dissection & explanation:
https://www.youtube.com/watch?v=V3-V00nhtpE
Yes, but there was a time where you didn't understand the risks of those things, either...so you learned, just as you are now with something different. It's all totally normal...and prudent, which is a good thing that you're showing here.
Really the risks are pretty small, but they aren't zero, and we're dealing with more packed energy than an alkaline or a watch battery, so respect and caution is good but I think as more of all these particulars sink in for you, you'll find that there's no reason to be scared. Don't go putting a cell in a vise or driving nails through them, and if you ever get a light that uses more than one cell, do observe the minor cautions there about discharge limits and not mixing cell types and whatnot, but overall with normal use and care, no worries. And a lot of our best-practice rules with cells have as much to do with getting the most life/most power from them, too, not just any inherent risks.
Dropping isn't usually unsafe at all, just the risk of making the light not work. With most lights the host provides more than enough protection for the cells and unless it's a really hard impact directly on one end the spring(s) are usually enough to cushion the cells from taking damage that way although it's possible that they could get dented or the driver in the head could get cracked/damaged in some way. With the low voltages we deal with here, flickering electronics aren't really a safety issue but I suppose with some designs there would be the potential for a short to cause unregulated current to flow...which would mean heat output...not so good for pockets or inside of backpacks or possibly the electric components with high powered lights. Like with some recent ones people had buttons stick in the on position or poorly made LED connecting wires that let the light run free...not from a drop but the same results essentially.
Now...if you drop a battery and it gets damaged from the impact, then some caution is prudent. The metal cans they are made from are quite thin, so they're easy to dent, and if that dent is deep enough it can push together the layers (jelly roll) inside and possibly cause a short, which would make the cell heat up, probably vent a little gas from the positive end, and hopefully not any worse (usually not any worse). In the CPF thread you linked (again, different type of battery there) he said the positive end of the battery hit hard and dented. Since that area is where + and - meet close together, there's a lot of potential for an accidental short to occur. There's a thin rubber gasket that separates the + and - in addition to the plastic wrapper on the cell that provides some insulation/separation. If the metal were crushed so much as to make the two meet, then you get a short. Or it could crush inwards and damage the CID protection foil or just separate the + end from its crimp, exposing the guts to oxygen. Again, usually a small risk/effect, but it's there. This is largely true for NiMH and NiCd cells, too, even silver oxide cells, but we just pack more punch into lithium-ion cells. So try not to drop cells and if you do, let them sit for a second before picking them up, and then inspect them for damage. Little dents are often just fine (and in fact, some lights will dent the ends of cells just from normal use if they're just a tad too long for its design). If the wrapper got torn, it's easy and smart to change that and you can buy wrappers super cheap, just takes a couple minutes to do that. If the cell starts to get warm or hot after a drop, chuck it outdoors onto concrete or something, just in case, but you're not usually going to see that. Again, if a light is dropped then the cell(s) inside are normally not at risk.
The everyday products you mention still have risk, too, of course. I'm sure you've seen many news stories over the years of laptops or scooters or juice packs erupting in flame or melting the devices. Most of those these days are a different lithium type but there are still several. Basically it's the same things happening where impact may cause a short...although shoddy electrical designs cause a lot of that as well, and even devices with built in protection circuits of varying types are not totally immune from risks...the combination of engineering and protections just minimize them to where hopefully it's just accident/abuse that causes problems.
For me, long ago I just adopted a policy of caution and observation - respect - for anything battery powered. I once pried open a tiny LR44 silver oxide watch battery just to see what was in there. Black dirt, basically...not so exciting. I put it in the trash can and moments later was headed out the front door to go do something. I smelled something...smelled like burning paper...and I'll be damned but the little opened battery in the trash can had gotten so hot with exposure to oxygen that it began to burn the paper towel that it was wrapped in! Glad I caught that before I left. Avoidable? Totally. Between that and some oopses while disassembling lithium battery packs and the many many stories of battery accidents over the years, I just pay attention now in how I handle them, stay present when recharging them, etc, etc. It's easy and while maybe not necessary or sometimes a slight hassle, it's prudent just in case. No fear, just a healthy respect (although I probably should have been afraid in the past, seeing as though I acted pretty boldly at times....). :)