Yeah, as many others have said, get a $10 multimeter that will give you far better accuracy in voltage measurements than any flashlight will.
Lights like the BLF Q8 will give you a rough estimate of voltage, but mine blinks out a reading that is about 0.1v - 0.15v too low. YMMV.
If you really did charge those cells to 4.5v, I’d be very careful about using them. They might be okay, or they may have been damaged. It’s difficult to tell. At the very least, charge them to 4.2v and let them rest for a couple of weeks. If they drop below 4.15v over those weeks, they’re probably damaged. Running a capacity test on them is also a good idea, but it sounds like you don’t have the equipment for that.
You can safely charge to 4.3v, though it will cut down the number of cycles you will get by about half. Higher than 4.3v is unsafe, IMO. If you’re concerned about safety, it’s probably best to get rid of those cells.