Hi Laura! Don't have answers to all the questions but will try to help with some. Bulb wattage will depend on your enclosure size and the max limit of the fixture. If 60W day/50W night keeps it at desired level and your room temp is stable, your done. If for any reason you need more heat; then you can trade day bulb for a red one (frogs don't see it) and test various bulb wattage combinations (both on at same time) until you get temps right.

No idea on UVB recommendations, and as you stated, it's not needed. If still using, you have to consider the heat that bulb will bring into your habitat temperature equation so don't end up cooking your frogs .

You can raise humidity by partially covering screen with saran wrap taped to edges (keep saran 1/2 in. away from hot fixtures). If your enclosure is an Exo-Terra type; they have cross flow ventilation front to back. You can safely cover front screen half to help increase humidity. Just keep an eye on frogs first few days to ensure they are OK with it. A shallow dechlorinated water dish in enclosure will also help maintain humidity. At present I do not use misters so will let others comment on that.

I spot clean tank daily and replace water at same time. Once a month the whole substrate is replaced with new coco (Plantation Soil). Have no worries of substrate becoming water logged from spraying (even if heavy) because I use a modified false bottom in my enclosures. For more information on those, see the forum's Red Eye Tree Frog Care Article: Frog Forum - Red-Eyed Leaf Frog/Red Eyed Tree Frog Care - Agalychnis callidryas . Good luck !