1.5 inches is, in my opinion, a lot. But, to answer your question: Yes, I would be concerned that the python will burrow and burn. These snakes do burrow and I have no idea why they would not burrow into your substrate. I would decrease the amount of substrate and decrease the temps.
Also, I would strongly suggest that you get a thermostat right away to control the temps of your UTH. Popular brands include Helix, Herpstat and Ranco (?). I use both Helix and Herpstat and have found them both to be reliable and easy to use.
Humidity should be between 50-60% per most members on this forum. I use to bump humidity to 72% for shedding until one of my snakes surprised me with a shed (didn't even know she had been in blue!) Her humidity had been 56% the entire time! So, I am now keeping my humidity at around 55% and bumping to 60% for sheds. I have 2 more in blue right now so we'll see how that works; I am expecting successful and perfect sheds!
Anyway, there you go. There are lots of ways to keep these snakes but the true basics are proper temps (thermostat), proper humidity, and proper hides. After that, your snake will let you know what he likes specific to his own personality~ and this just takes time and observation!