I went back through the entire thread.
I don't believe you caused "mild scale rot" in the short amount of time in the conditions you have described. If anything I would have thought you were setting the snake up for an RI. What makes you believe it is scale rot? I think it sounds more like a burn but without being there or at least seeing some pics we are all guessing here.
You need to help us help the snake. The snake is not causing this, you are. If it were me I would be living on the BP.net and checking every post my thread got and giving a play by play of what is happening in the attempt of creating the correct husbandry for my snake.
While I may be with the others agreeing its time to see a vet the issue of husbandry is going to still be an issue at home and needs to be addressed. Without fixing it the snake has no chance of making it. If the vet is not an option because of money it may be time to suck it up and pass the snake on to a more experienced keeper. It sucks but you really need to do what is best for the snake and you and your sis have not been achieving that. Im not trying to be rude or make you feel bad. Im just trying to do what is best for the snake.
I am here to help and will continue to do so. We need you to step up and do what it takes to make things right. You need to buy the proper equipment and get a proper setup.
Lets start over on some things:
What is the setup right now? How is the cage setup? Pics would be best(top view too.)
Did you get a mister or fogger?
Do you have a temp gun?
Whats the humidity staying at?