Any cool mist humidifier will do. But we happen to have an elephant and a pig for our two bedrooms. Just to show you what I mean:
http://www.google.com/products?clien...&oe=utf-8&um=1
We like it b/c there are no filters to be bought. But I'm sure you can find them cheaper somewhere. We got ours at Bed & Bath.

The foil sounds like a good idea - and all your layers on the bottom. Our BP is our 6 yr old son's and we fell in love with her, too! She is on her 2nd course of antibiotics right now! Yikes!

Anyway, about the dimmers, etc. My husband cut in a dimmer for the UTH b/c he knows some electrical. They are about $6 bucks for materials vs. $25 for a rheostat (which is the same thing, but no electrical work or knowledge required; and it's UL listed). The thermostats take the temperature and dim the heat source up and down to maintain a steady temp. We love ours for the CHE! But it was $19.99 on sale 1/2 price and we can't find any more of them right now. We want one for our other snake's tank at some point, too.

Did we talk about insulating the outside of the tank? Two sides of ours has 1" insulating foam around it and that helped a lot, too. Three sides of the tank would make it even better.

Sounds like you are on the right track. Good luck!