WOW! 10 pages of posts in two days on a tank set-up. But it's all good.

Here's a few things for consideration that I didn't notice mentioned yet.
In addition to a bigger UTH, you can get this stuff from Target or Wal-Mart called Foam Core Board or something like that. It's usually in the school supplies section near the poster board, and it looks something like a cross between styrofoam and cardboard and comes in different colors, or, you can use regular cardboard or styrofoam if you choose. Cut it and tape it to the ends and back side of the tank. This will help insulate the tank some and help keep some of the heat in.
Depending on what type of room the tank is in, you can opt to use a space heater to keep the ambient temp of the room itself at around 80F.

Regarding rheostats and dimmers: I got my first snake and set-up in the winter, and initially was running the UTH on a rheostat and the heat lamp on a timer to cycle it on and off and this was working ok. However, once the weather started warming up, I found it harder and harder to keep the UTH temp where I needed it, and it finally got to the point where just turning the rheostat on at the lowest setting was letting the UTH run at about 96F, and it was only Spring. That was when I finally invested in a Ranco and never looked back. So keep in mind that as you run your house AC/Heat, and weather is also going to affect your temps.

As you have found, doing a new set-up takes alot of tweaking to finally get everything dialed in right, but it feels good once you get it.

Have fun picking out your new pet...