Try a modular approach working with temps. For a screen top tank, you could cover a portion of the screen (on the hot side) with some duct tape. I did this many moons ago for my kids bearded dragon. Worked out really well for us. Make sure the temps you are reading are as close to the bottom surface of the tank as possible. Once you reach your goal, look at other items you may need to refine and in no time your snake's home will be fine. Best of luck.

Your snakes activity is on par for ball pythons.

One thing to consider is the current placement of the tank. Look around to see if it might be close to a A/C vent that could be throwing off the temps. You might want to move the tank somewhere else if that may be the case considering how cold the house is kept.