Revamp?!?! Any help highly appreciated

[Hugsplox]

How old & how big is your BP? A 40 gal. tank would be a nice size for an adult BP, but it's probably freaking him out (combined with the move) because it's too big, not to mention the trouble you're having with the temps. & humidity. If your BP is young, a hunger strike is not normal & can be dangerous for his health. You need to fix this asap.

Screen tops can be modified- covered most of the way with foil or plexi, or anything that doesn't allow for all that air flow. Fixing the humidity also depends on choosing a substrate that holds humidity, &/or offering a humid hide in addition to the cool & warm side hides.

Glass tanks can be insulated to keep heat in using all sorts of materials. That's not your biggest problem. You always want to set up a snake enclosure & test it out for a week or two, making sure the heat is adequate. It's stressing your snake to keep experimenting while he's trying to live there. Not sure about using an RHP with a tank, maybe someone else can offer advice about that, as I don't use them at all.

BPs are ambush-predators, NOT active hunters. Especially when young, they prefer cozy quarters- without that, they often refuse to eat due to stress.
Instead of a heat "lamp", try using a CHE (ceramic heat emitter) in a suitable metal dome- it puts out heat only, no light. BPs don't like bright lights anyway, & certainly not 24/7. And if adequate heat is a problem, you might want to keep the UTH running too- with the "warm side hide" over it.

I hope you know that ALL heat sources need to be controlled by thermostat for safety?

I think Bogertophis covered all the big hitter items about converting a 40 for BP use. You're gonna get people who tell me you to move to a tub because it's better, this isn't entirely true. You can make your enclosure work, and it can work well, you just to invest the time, and very little money into it.

Here's how mine was set up before upgrading to a PVC enclosure:

1. Three sides covered by black paper. This was to block off the sides to make the BP feel more secure, I liked how the black looked but obviously you can do whatever color you want. Around that I used something similar to this to insulate the tank.
https://www.amazon.com/Reflective-In...39809377&psc=1

2. Cover most of the top with a few sheets of aluminum foil, held down with duct tape. Again I used black here to match the rest of the set up. I left just enough space for an appropriate fixture, with a 100w CHE controlled by a thermostat which handled ambient temperature. A UTH under a hide also controlled by a thermostat took care of the hot spot, and a big water bowl on top of that warm hide. The CHE would heat the water up just enough to cause some evaporation, which helped maintain humidity, and misting once or twice a day maintained the rest.

3. Substrate is up to you, I used Forest Floor and Reptibark later, personally I prefer Reptibark but again whatever works for you. Lastly, either purchase or DIY yourself a humid hide. This can be done with a tupperware container big enough for your snake to get into, and some moss, or you can purchase a premade one online. This will give your BP a humid place to go in the event that it goes into shed, or if your humidity drops during the day.

There's nothing wrong with using a tub if that's what you want to do, but a glass enclosure is perfectly acceptable if you do it correctly. Plenty of clutter, fake plants, cork bark, multiple hides, you can make that enclosure work for him. It'll just take some effort on your part. Going out and buying a tub may be an easier option but considering he's already not eating, I don't know that moving him into yet another new closure regardless of reasoning is the right move.