New bedding is a definite must. Pine has oils that are extremely harmful to snakes and will only exacerbate any existing issues. I personally would consider removing the substrate and using a few layers of paper towels, both to keep the wound clean and easier to monitor, but also to replace the pine if you can't afford a better substrate.
Knowing the exact numbers for your Temps and humidity is also important though. Especially with an under tank heater. They are notorious for getting too hot and burning reptiles. Correct me if I'm wrong, but I assume that since you don't have temp or humidity sensors that you don't have a thermostat?
Some of these fixes are slightly on the pricey side, but it's going to be very important in helping your snake recover. I get money being tight. I'm a single mom that can't reasonably work until the schools open again. Still, if you take the responsibility for a life, it's up to you to either provide it with what it needs, or surrender it to someone who can. Just my two cents. I hope your baby gets better, and I hope you find a way to afford the needed changes.
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