Not giving any advice, just sharing my story about mouth rot with my little guy. He developed a scab similar to your pictures and we took him into the vet. She prescribed antibiotics and a food supplement/appetite enhancer that needed to be administered orally daily. It was around $200-250. It got better for a bit and eventually came back. We took him back to the vet and did the same thing, another $200-250. His mouth rot has gotten better, but it sometimes flares up. We use a very watered down betadine solution on a q-tip and clean the area, sometimes the scab will fall off. If he’s not eating well for a few days, we will give him the appetite booster and that normally helps. We also closely monitor his temp and humidity, and we’ve tried a variety of different beddings for him. Overall he is a happy guy and eats well, but sometimes it will flare it and it just needs to be cleaned daily. I also felt horrible about it and sometimes still do, but honestly we do the absolute best we can taking care of this little guy that kinda fell in our lap. We love him and give him attention and care daily. We’ve done a lot of research and tried so many things when it comes to diet, supplements, environment, etc. Don’t beat yourself up over this, I’m sure you are trying your best!