Cant get my tank to stay the same temp and humidity

[Namea]

It looks like you're really putting in the effort to listen to solid advice and that's awesome! Here's some good cheaphacks I've learned over the years. When I first started rehabbing snakes I wasn't very financially stable and since they weren't permanent pets I didn't care as much about aesthetics.

Hides:
In a pinch shoeboxes or tupperware with holes cut (and sanded) make great hides. Flower pots too. If all you have is one of those wooden half logs you can use cardboard or just make sure it's flush against the side of the tank to make it slightly more hospitable for a bp. You can also check thrift stores, craigslist, fb marketplace, or letgo. Lots of people give away pet supplies for free or super cheap! I've started checking monthly and stocking up for whenever I need to set up a new rehab enclosure.

Glass Covers:
Those old fashioned sticky book covers that they sell around school supply season are awesome for covering three sides of a tank. If not printer, construction, butcher paper, wallpaper, or the custom ones they sell at stores all work well. Aquarium ones are sold frequently. If you have a good printer or are willing to shell out like 3.50 at staples you can even find high res images for free online that are made for it and will print at the proper size already! Of course never put adhesive in the tank itself, only on the outside. My son is 8 and he likes to draw backgrounds for some of ours to use. It's adorable.

Screen covers:
Foil works swanky, cover most of the screen with holes for any lights you're using and an extra one for ventilation somewhere. Old shirts also work well.

Substrate:
Looks ugly but newspaper and paper towels are cheap and won't hurt your baby. Again, old shirts could work too. Coconut husk bricks are cheap on chewy or amazon (so petco will price match) and they retain humidity well. Freeze the whole brick for a bit before you follow the instructions to expand it. Looks nice and is safe. It doesn't need to be deep, contrary to popular myth ball pythons aren't burrowers, they like hides but they don't need to be able to dig under the substrate and make tunnels or anything.

Dish:
Rock dishes are popular and pricey but they look nice. For a cheaper alternative most dollar tree stores have nice heavy ceramic pet bowls that are big enough and won't be tipped over. Make sure to scrub it once a week and keep the water refreshed. Bonus points if you get one with a paw print pattern because it'll confuse people. You only need one. Some people prefer to put it on one side. I put mine in the middle for bps. While bps aren't aquatic they do sometimes like to soak bits of themselves. The dish doesn't need to be big enough to fit all of them but big enough to have a lil dip once in a while doesn't hurt.

Decor:
Fish tank decor and clutter are good and cheap. BPs like clutter, it may seem odd if they can't like fully stretch out in a big open space but they like it like that. They aren't technically arboreal but some like to climb. If you choose to use a found branch make sure you wash and disinfect it. Make sure it's not a sap-heavy type of wood and bake it or freeze it to be double sure there's no bugs. Sand down any sharp bits. Lots of places online sell branches pre-treated for reptiles that are cheaper than the driftwood crap you'll find in pet stores.

Thermometers/Thermostats:
Amazon has some great deals. I've personally used all of the following with great results:
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They're all under 15 bucks too!

Heat/light
BP's don't NEED light per-se. Underbelly heat is best for them but some uvb never hurts and some light to help with ambient temps doesn't either as long as it's not killing your humidity. Make sure you have a regulator for any uth you have. In general if you touch the bottom of the tank and it's uncomfortably warm for your hand, it's too hot for a snake. A little warm is okay but not hot. Never use a heat rock. Even the better brands that don't get too hot are worthless because in order to not be too hot they just don't really warm up at all and it's basically a waste of money. If your snake wants to bask they'll find a way. BPs aren't super sensitive to day/night cycles but again, it doesn't hurt and might make them a little more comfortable so a timer can be useful but not necessary.

Uhh...everything else has been said way better by others.