1) Bump up the hot spot to 95.
2) Lower the humidity (heat + too much moisture = bacteria breeding frenzy)
Keep the enclosure simple and hospital sterile. Maybe change substrate to paper if you don't already use it.
When you go to the vet, make sure they take a culture in order to target the type of infection. Without a culture, it's difficult to pick out the right antibiotics that target that specific infection. It's a shoot in the dark otherwise.
If they offer you oral medication, request for injectables. Snakes have very slow metabolism and oral meds are very ineffective.
I'm so sorry this happened to you. I'm happy the snake is finally getting the care it deserves.