Hello Justin, I'm Dr. Deb and I'll do my best to help you today.
I'm sorry to hear that Baxster is deaf.
Deafness in dogs is classified as either acquired or congenital.
Acquired deafness may be secondary to ototoxic substances (gentamycin for example used in the ears to treat an ear infection), chronic exposure to loud noise, hypothyroidism, trauma, or neoplasia. Old dogs can become deaf as part of the aging process.
Most likely, none of these causes apply in this case.
Congenital means that he was born this way. Dogs of any breed can be born with this defect although there are a number of breeds that are at higher risk for it such as the Argentine dogo, Australian heeler, Australian shepherd, beagle, border collie, Boston terrier, bull terrier, cocker spaniel, Dalmatian, English bulldog, English setter, foxhound, fox terrier, Norwegian dunkerhound, Old English sheepdog, Scottish terrier, and the Sealyham terrier.
If you wanted to have him evaluated, you'd have to take him to a specialist. The testing equipment that is done to evaluate possible hearing loss is not something that a regular vet would have.
But most likely, if you think he is deaf, he probably is and will remain so for the rest of his life.
This doesn't mean that he can't be a wonderful pet and live a long and fulfilling life. It just means that you will have more challenges in training and living with him. Living with a deaf dog is not for everyone since it requires a tremendous amount of patience and time but it can be immensely rewarding.
This LINK should help you understand what's involved in living and training a hearing impaired dog.
I hope this helps and I wish you the best of luck with Baxster. Deb