I used to have humidity issues as well. I went to Lowe's and purchased a $10 piece of plexiglass (cut to fit the top) and that resolved all of my hunidity issues. It never gets below 50%......NEVER. As far as substrate goes I use outdoor carpet from Lowe's as well. I got 4 pieces of carpet for under $3. As a result, I do not worry about my ball python ingesting anything other than a mouse.

I also only use a UTH......I do not use any heat lamps. I use a tube florescent light for my viewing pleasure but that is its only purpose.

Good luck!