If you're going to go the branch route, I'd suggest going out and getting him one of those grape branches because they'll hold up his weight as he gets older.
The thermostat probe should be on the exterior of the or the terrarium sandwiched between the RHP and the glass. If you have it INSIDE the terrarium then the glass will heat up to the 102 F. It might not only crack the glass, if your BP ever gets under the carpet, he will burn himself. You can get small furniture pads and put them under your terrarium so you have a small clearance between the terrarium and whatever it's sitting on.
I'd also get rid of the reptile carpet. That thing breeds all sort of grossness especially when he poops and pees on that thing multiple times. With high humidity and heat, you're creating a breeding ground for bacteria. I'd personally suggest coco husk because it holds humidity very well.
Here's a great thread of how to set up a glass terrarium just in case you didn't have a chance to check it out:
http://ball-pythons.net/forums/showt...-With-Pictures!