Most people will tell you to be careful with any kind of sand, but some agree that sifted playsand is acceptable. I see no need to take that chance, so i keep mine on shelf liner/paper towel.
It seems like once you get some ventilation, you may be better off. The basking light should be...
What is there for ventilation? Is the tank a screen top? Also keep in mind that temps of 100-115 can seem very warm to the touch on a cool evening/morning. You are correct in turning the lights off at night.
What substrate are you using?
If the whole tank temps are too high, they will find...