Hey Vanthios

First off, thank you for taking in this bp, sounds like it has had a hard upbringing so far. Everyone on here has given some good advice, but I can see how it could be confusing and or expensive being put into this position of having to remediate care for the snake so quickly. Im going to give you what I consider to be a 'back to basics' simple approach for creating a sufficient environment for the snake, with the least possible cost involved. IMO its best to start out this way, and then you can tweak and modify as you get to know the snake better.

For this situation I would recommend using a heat pad as your only source of heat. I saw that you mentioned that the one provided was small compared to the tank it came in. I would also venture a guess that it might be old and possibly not holding temps that well. You are going to want to get a heat pad that is around 25-30% of the area of the floor of the cage. To regulate this, I like to use a simple lamp dimmer switch from home depot, which runs about 10$. To accurately check the temps of the pad, an infrared heat gun is an absolutely necessity, no matter which type of heat source is used. You can pick this up online for around 30$ or less I believe. With this method you plug the heat pad into the lamp dimmer, and then modulate the temps to achieve around 90 deg hot spot, using the infrared heat gun to calculate temps. As long as the tank is in a room that doesn't have wild variations in ambient temps, this should do just fine. A thermostat is always a more accurate way to modulate temps, but a good one will run you close to 100$. Save your money.

Next, you are going to want to limit ventilation on the screen top of the tank. There is a DIY guide to this in this forum. Basically it consists of using aluminum foil and duct tape to limit the amount of ventilation in the tank. This traps heat and humidity in the tank, and prevents it from escaping. If ventilation is properly controlled, your humidity and ambient temps should be fine without a heat lamp as well.

It sounds like you already have a couple hides, place one hide over the heat pad on the hot side of the enclosure, and one hide on the cool side. I like to put the water bowl in the middle of the tank. For me, using paper towels as a substrate works great initially, especially when the health of the snake is in question. You can add items to clutter up the tank, but we aware that anything that goes into the tank, must be cleaned appropriately.

As your snake is ready to shed, I would recommend making a humid hide for him. You can achieve this using a Tupperware container, cutting a hole big enough for the entry and exit of the snake, fill with damp sphagnum moss (also at home depot) and place in the cool side of the cage. Some like to leave the humid hide in indefinitely, and some just make it available during a shed.

To me this is the most sensible and realistic beginning enclosure for a recently acquired snake. Make sure to check the temps regularly, and look for signs of mites and any other signs of disease.