Good planning on the screws and wing nuts. I'm sure a few of us have wished we had something that secure at one point or another.

I wouldn't buy my thermometer at RadioShack if I were you as they tend to be quite expensive. If you can, go to Wal-Mart or Target and look with their standard outdoor thermometers (typically near hardware or garden), and you should be able to find a digital indoor/outdoor thermometer/hygrometer combo with 10' probe for under $20. Mine was $14.88 at Wal-Mart. I'd rather have 3 for the same price from Wal-Mart than one from RadioShack, personally.

Until you've purchased your thermometer and have it set up taking floor temps, I would not worry about the temp of your heating pad. The goal is to get the temp on the high side to about 90-92F, and since your temp should be about 98.6F, it won't feel especially warm to you.