You need to get something to regulate the UTH, so on your budget, go out and pick up a lamp dimmer from Home Depot, Lowes or Walmart. They're about $8.

Don't worry about the snake moving the hides around. I have one who just moves her hide wherever she wants to be in her tub. You may want to add a second hide on the other side of the tank though.

You can also pick up an Accu-Rite Weather Station from Walmart for about $12. That will measure cool side and warm side temps as well as humidity. It's a digital one and much more accurate than those sticky dial types you can get at the pet store.

Not sure how much a shirt laid on the tank is gonna do for humidity. I would recommend covering 2/3 of the screen with tin foil and use tape to hold it on (outside the enclosure of course).