The big three I pay attention to are:

1. Ambient (80F) --- I know literature and info online suggests that ball pythons can sustain temps down to 75F, I have had bad experiences with older snakes going below 80F (my only RI I have dealt with).
2. Hot Spot (90F) --- I think it is nice to have.
3. Water Bowl --- Large/deep enough to comfortably soak in.

-You are running warm/cold sides. I prefer to avoid this method even though it works fine if the enclosure is large enough.
-Your hot spot is 86-90F. In the past I kept my hot spots at 85F and I would get a regurge every now and then. Ever since I bumped my hot spots to a stable 90F: I have not seen a regurge in years.
-I struggled with humidity for the longest time and I think I did more harm than good artificially raising the levels. I live in New England (not an arid climate) and a large water bowl at target ambient temp (80F) seems to work fine for me: I pay no attention to humidity for my ball pythons: they can soak if they like.