If it helps, this isn't "real" aggression. This is a dog with a lower bite threshold doing exactly appropriate behavior when he feels threatened or wants to discipline your son for extremely rude behavior (for a dog, hugging, taking food away, tugging on collar, etc. are insulting, threatening, and bad; they tolerate it from higher-ups but not from pups or dogs in subordinate positions). The dog is making normal doggy choices--but his "cross this line and I'll bite you" border (which every dog has, but some are set very high and some are low) is set at an unacceptable level for your house.
What I am sure Shannon meant by this is a tough one is that the best solution for this dog is to not be put into these situations. He's had a certain set of rules and expectations for his whole life; it's not his fault that he now has a pesky "puppy" pushing all his buttons. His responses are understandable.
Training commands is not going to help. Where obedience may come into play is if a good trainer can help you find an effective position of dominance over this dog so that you can throw your mantle of dominance over your son--even adult and settled dogs CAN come to understand that they must tolerate rudeness because you have decided that the annoying puppy must not be messed with. So I would seek out a very, very good trainer, not just any obedience class. Neutering ditto--not going to change normal dog behavior, though it can help with some male-to-male fighting and wandering.
Household management also becomes key. Avoiding triggering situations is only fair to all concerned. If you can supervise the interaction and keep your son from doing the things that you know will be problematic, they can be together. Otherwise, either the dog or the kid needs to be behind a baby gate. The dog should be crate trained for his own security and safety.
And then you pray for your parents to come home soon!
yeah, what Joanna said, it's tough as this dog has been raised one way...if this was a case of "we just got this new dog and this is what he's like" then you put a TON of work into changing what for the dog has always been, but, we're talking a year of training, and hard work and committment when the dog may well go home a month from now, kwim?
Realistically, it depends on how much you want to put into it..if it were me, I'd get a good crate and set some house boundries both for your son and for the dog.
I wish I could give you a way easier solution.