I’m not quite sure what you were expecting. 840 lumens is a very high output and therefor requires a lot of energy. You could upgrade the battery to the new 18350 1200mAh battery available on the market but still can’t compete with an 18650 battery. I personally would have liked to see the 205 lumens mode bumped up to 300-350 which should provide a good middle ground between having a decently bright headlamp without needing the full output of Turbo mode and wasting energy.
I don’t think a 1A or greater would even matter because it sounds like the light decides it’s own current, which is less that 0.5A. Because otherwise the 0.7Ah battery would take only an hour to charge at 1A.
Love the photos. They look great and even the beamshots look very crisp. How familiar are you with Kelvin? I was wondering if you are able to give an approximation on what you thought the temperature of the light is.