I'd be pretty pissed if my snake came back from the hospital with more problems than he went in with...problems that are EASILY preventable with simple cage fixes. That's simply ridiculous.
The first picture looks more like a puncture wound than a burn, but I couldn't really picture what you were trying to describe it living in and have no idea what kind of wound his little "mini escapes" might have caused...maybe a combination of a burn and puncture. Antibiotic ointment (without any pain killer in it) should be enough for that, but keep an eye on it.
The second picture looks like the very early stages of scale rot, to me. Clean, dry bedding to prevent it from getting any worse, and it should shed off with the next shed.
I STRONGLY recommend getting a reliable thermostat to control your heat pad. Relying on layers of substrate to both maintain proper temps and keep your snake safe from burns is just asking for trouble.
I also highly recommend keeping him on clean paper until all signs of wounds are completely closed up and healed. Plain ol' newspaper or paper towels is fine. But, you'll have to have that heat controlled first!
Keep in mind, none of us are vets and can't diagnose your animal over the internet. If those injuries happened at the hospital, then you should be able to follow-up on them without incurring any extra costs...but I would NOT allow them to keep him overnight again.