yeah, this is a really serious problem – talk to a trainer and/or behaviourist. My dog had a similar/not identical problem, where he was jumping up and biting me and tearing at my clothes when he got overexcited. He thought he was being playful, but I was covered in bruises and lost some nice sweaters to his teeth. I consulted with a trainer and a behaviourist (am still consulting, still doing obedience classes, etc) and it’s gotten much better.
Some short-term stop-gaps that might help: on his walks, try him on a gentle leader or a halti head halter. They’re recommended for dogs who are developing aggression because they allow you to control the dog’s head – this is how I got my dog to stop jumping up and nipping/biting during walks. They’re not a solution, but they can put you back in control while you get your dog trained.
The other thing to consider is that dogs who growl/bark/bite at everyone EXCEPT their owners/families often think that they’re in charge, and are trying to protect you/mark you as their possession. This is often why small dogs are such jerks, and are only nice to one person; no one ever trained them to know that they weren’t the head of the house. Thinking they’re in charge is bad for you and bad for the dog – you aren’t in control, and the dog feels more anxiety and worry because it’s his job to protect everyone. Here is a good article on getting back in control:
http://www.shirleychong.com/keepers/mindgames.html
I found it really helpful.
