Sounds more like mouth rot than a RI, and it can lead to worse infections such as an RI. Please make sure you sterilize EVERYTHING he is in and you touch before and after. I took a boa in years ago with a 'cheese' mouth that had to be pried open every time, and with antibiotics, we did oral back then and I think that helped with it being somewhat topical where the infection was, and I irrigated it twice a day gently with a syringe and lactated ringers. Eventually he got his mouth back, all infection subsided, and after a year of not eating he did, finally, on his own, after I had him for two months. He was a nasty tempered old man, but who could blame him. Might talk to the breeder on this one, it might be a result from injury in attempting to assist feed, too. Good luck!
*Fila*