That is a pretty big tank for a BP, especially if its still young. But if you are going to use it, I will try to answer you questions.
Instead of "hot glue", I would use 100% Silicone! Lasts for years and is flexible unlike hot glue. Thats what they use to make aquariums. Before you silicone the lid down, you have to prime the plastic frame first (just where you are going to use silicone) so the silicone sticks the the frame better. I think Acetone will work, and maybe fingernail polish.
I would not recomend putting any heating device inside the tank with the snake. The snake will end up touching it. No good could come of this. Instead, maybe be you could put a piece of flexwatt some where on the back and run that through a thermostat. That would help raise your ambient temp., just a thought.
Now for your last question. I would pull any loose sealant off and go over all the corners with the 100% Silicone. Just put down a small bead then go over it with you finger tip to spread it out. Give it a good 24 hrs. to cure. The 100% Silicone you can get at any hardware store, just make sure it says 100% Silicone. And you will need a caulking gun.
hope any of this helps,
Dave
Thanks!
I was planning on sectioning off some of the tank since it's so large.
And I have a caulking gun, so I'll pick up some silicone!
1.0 '12 Irian Jaya Carpet Python
0.1 '09 Normal BP
1.0 '07 Normal BP
1.0 '08 Pinstripe BP
0.0.1 Nelson's Milk Snake
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0.2 Horses (Egyptian Arabian & Tennessee Walker)
2.2 Dogs
1.1 Cats