re: Just purchased my first gun safe. A few questions

I wouldn't put anything down. I would just leave it on the carpet.

Ideslly, they would have a home in the back for you to run a couple cords through. If not, there are several options for moisture absorbing packs. I think you just put them in the oven every once and a while to dry them out again. I would also put a touch light in there if you can't run a real one.