I don't have quite as big of a tank but I definitely dealt with the humidity issues. I have a ceramic heat emitter and I was spraying my tank 3 - 4 times a day. Within an hour the humidity would be back down to 20%. I live in a desert so the air is very dry.

Personally, I bought a reptile fogger. I've heard mixed things from people on them but I turned mine on the lowest setting and set it up with a humidity gauge. The fog that comes out vanishes before it touches the bottom of the tank so there's no fog in the tank unless I turn it up which I don't do. Now his humidity stays between 53 - 58% at all times. The reason I tried this is because I bought him very young and I had him for three months with no shedding. About a week after I added this fogger there was a perfect snake skin in his bigger hide. May not work for all, but it worked for me!

I also stay away from heat pads. if your snake burrows under the substrate to the heat pad, he might get burned if the temperature below the substrate is too high. I personally prefer overhead heating. I put foil on the screen lid (which it seems you don't have) and cut a hole for the heat emitter and to allow air flow.

Another option that I have used to great success is insulation! I bought foil insulation off amazon and wrapped the back and sides (with your tank you can even do part of the top where the heat emitter isn't set) and it'll insulate the tank and keep it toasty inside. It'll also make it so that you don't have to have the heater on as much because it holds the heat in. It's not the most pretty thing in the world, but if you use decorative duck tape, it's not so bad.

I'm still a newbie with ball pythons, but this has all worked for me, so maybe it'll help you! Hope it helps!