1. As long as the snake can not crawl up in there its safe, I'm assuming that goes over a screen lid.

2. With all 3 of those on, there's not much of a thermal gradient. How does the ball get to the heat? Ball pythons spend all their time on the ground. While those bulbs will help with the ambient air temp, I'm not sure how well they'd heat the surface of the cage. You'll have to play with the setup to get it right.