Hi A.. I second the advice given to you by several others to find a good trainer, preferably one with breed experience, to evaluate the situation in person and provide you with guidance before you consider re-homing the dog. In the meantime, however, it would be a good idea to make sure your son and the dog are both closely supervised when they are in the same room and to never leave your son alone with the dog. We took a class on "introducing your dog to your baby" before our daughter was born, and that was the number one piece of advice the trainer gave us - no matter how well you think you know your dog and how sweet, friendly, and well-behaved your dog is, don't leave your child alone with the dog, as things can happen in an instant.
The class also had a lot of good advice on how to treat your dog with respect once a new child enters the picture and how to understand and deal with natural feelings of jealousy (after all, the dog was your first baby!) A lot of these centered around making sure the dog has a safe space to go, where he knows the baby is not allowed, and really respecting these boundaries, as well as respecting the dog's personal items (like food). We also learned a lot about how to approach dogs "politely" (i.e., from the side or below, never looming from above or coming at a dog straight on), which we plan to teach our daughter when she's a little older.
If you're in the Raleigh/Durham/CH area and would like the contact info for an excellent trainer we've used and also of the person who taught the class (I believe she published a book as well), just message me privately, and I'd be happy to dig those out and send them to you. I can sympathize with your situation - when my daughter became mobile, the more high-strung of my 2 dogs also did not react terribly well, although fortunately we haven't had to deal with a biting incident! Oh, and just to weigh in on the "boxer debate," I come down firmly on the side of boxers being amazing family dogs! Our boxer was 8 when the baby was born and had never been around kids before - but knowing that boxers have a reputation as being terrific family dogs, we weren't at all surprised that she loves our toddler and lies quietly while my daughter hugs, kisses, and generally climbs all over her!