I haven't used any UVB light for my RETFS in the past 4 years.
Feed around 6 every 2-3 days for my 3 RETFS (so around 2 big crickets per frog every feeding no longer than space between eyes). I find that if I feed more they can't finish, mine don't seem to be large eaters for some reason.
I don't find them difficult to keep as sometimes my humidity (HK is pretty humid) is very low in winter and they have been fine. I've kept them in temps between 18-31 degrees celcius, sometimes turning on a basic fan in the room or room heater when the temps are borderline touching their min-max range.