Sounds like you need a thermostat- this is NOT a "temp gun." It sounds like, from your description, you aren't using a thermostat at all. This will cost you some money (like $50?), but will fix your temperature problem. I have two JumpStart thermostats (different setups, not in the same setup) and have not had issues with them. They are more expensive, but are not going to be garbage. UTHs, I have used Flukers, not sure which brand is "best" but haven't had a problem with mine. Maybe you got a bad UTH; whatever, they are pretty inexpensive. Get a different one. And attach it to a thermostat! You could kill you BP if you don't use a thermostat, and also, you know, burn down your house.

So,
Watch this video: https://www.youtube.com/watch?v=7EDX59Zlto4
- Get a thermostat (like I said. This is not a temp gun. It plugs into the wall, and the UTH plugs into it.)
- Get a new UTH and plug it into the thermostat
- Hides; you haven't mentioned having any
- Don't feel bad not using the tank just because it was a gift. Clearly whoever gifted it to you didn't research. Your animal's life is more important than gifter's feelings or whatever? Personally, I say you will waste more money "upgrading" an inherently unsuitable tank when the alternative is better and cheaper. You say you are stressed about the humidity... Then get a better enclosure.
- You can get a plastic tub from Target, which would be like, idk, $10 maximum? And it would be better than the tank you have. I would recommend this instead of just putting something on top of the screen to hold in more humidity, because a tub would be a more long-term solution. Also, because you have like totally freaked out your bp, it would feel more secure in a tub. Some people keep theirs in only tubs.

And just saying your UTH is a bad one, doesn't mean you can't/shouldn't use one; go get a different one. I can't imagine leaving a light on all the time or turning it on and off periodically. That really bugs me, and is torture for your snake. That alone would cause a hunger strike.

Actually while I'm at it, just watch this too: https://www.youtube.com/watch?v=rNpljc5aH1k