Wow, that sounds awfully serious.

One question, how do you heat his tank ? And how is the heat regulated ? Just in case it might be a burn. That seems to have gotten very bad very quickly. Scale rot is usually caused by excessive moisture, do you have a way to measure the humidity in his tank? Do you mist the bark ?

For now don't let it get wet if you can help it. The moisture is only going to irritate it more. Try to keep him as dry as possible. You can use the polysporin if he'll tolerate it. It is very good you are going to a new vet, he's going to need a lot of help to recover.

I wish you all the best. Try not to give up hope. I've seen pictures of some horrible things here, and usually the snakes make it through with good care.

Gale