My apologies that you are going through this. I had a breeder spat with one of my english bulldogs before. ( my bulldog past away 2 days after we bought him). First thing I would say personally is that I would return the puppy for a full refund. I know you guys are attached but this might be the best option. I would also schedule a complete BAER test. If the deafness is in fact congential, contact the breeder with the results and tell him that you want your money back ( or whatever refund you and your girlfriend wants) if he doesn't oblige contact the AKC immediately ( you might even want to contact them right now). They are going to ask you send them the letter detailing what is going on and the results of the BAER test. If the breeder still doesn't obliged you might want to call a lawyer. Unfortunately this is what we had to do just to get half of our money back. What does the contract says. Does it states a 1 year health guarantee. Have a legal person read it over. That's what i did and although they were "guarentees, and good health written in the contract", my contract was pretty much trash. and this was from a supposedly top notch breeder
Rereading your message again. Make sure you detail everything to the AKC, there motto is that they do not get into breeder and seller issues, but please be vocal and let them know what is going on. How does the breeder sound on the phone? hostile upset? does he seem like he's willing to work with you. If not I wouldn't expect to much from him. Also did you register the puppy already with AKC. I don't have much background with dealing with deaf english bulldogs, however i did have deaf great dane
Sorry for rambling but I went through this just a year ago, it was the longest drawn out 5 months.