Personally I have a space heater in my snake room set to 72F, that's the ambient for the cold side. I also set my hot spot to 88F. I actually remove all the substrate over the hot side so the snake is directly on the tub, then I put coconut husk substrate all around him for humidity, but he sets directly on the bottom of the tub. If he makes a mess I clean it up with dilute Chlorhexidine solution and wipe it out with paper towels, and I only spot clean the substrate around the snake if it gets dirty. The bottom of your tub should be the same temp as what your thermostat says since your thermostat sits directly under the tub. Anything over 92F can cause sterility in male ball pythons. Most texts recommend a higher temp and people will repeat that incorrect temp of 92F. Most breeders now will recommend 88F for the hot spot. I don't have any problems at all with the lower temps, almost all my snakes eat on a regular basis twice a week. I usually mix up the rodent sizes based on what I have in my rodent rack, so sometimes they get a big meal and sometimes a small meal, works great for feeding twice a week.
I'm thinking you have a bad thermometer or something if you are setting your thermostat high but your hotspot under the substrate is low.