1. If I use flexwatt heat tape can I jus put it under the cypress mulch substrate that I want to use?

~~When people use flex inside an anclosure, they usually cover it with some
sort of tile or linolium.

2. Will making the rear wall out of peg board (i think thats what its called) loose too much humidity?

~~ It would probably depend on where you live, imo if using the peg board
you could use the press & seal to cover some of it if humidity becomes
an issue

3. Where is a good place to buy flexwatt heat tape?

~~Beanfarm.com or reptilebasica.com

4. Is glass better that Plexiglas and if so why?

~~I think it's a preference thing, plexi won't break

5. Do the repti glo backing infrared lights also give off UVB rays?

~~Dunno, don't use it

6. How should i position fluorescent tubes so that my snake wont mess them up?

~~At the top of the enclosure