From the description and pic I don't think that's scale rot especially since you said your UTH is getting to 125F. Plus the blisters now.
I'm not sure why you keep saying it's scale rot when everything points to burn
I'm also hoping that since you keep saying it's scale rot that you didn't put off on ordering a t-stat. The sooner you do that the sooner your little guy can start healing.
Sorry didn't think my works correctly but I just finished ordering the Hydrofarms t-stat. I'll try to find a good herp vet ASAP.
1.0.0 - 100% Het. Pied (Cthulhu)
0.0.1 - Wild Caught Desert King Snake (Pickle) Gave it away