I'm not sure about where you live at, however around here there are some dog trainers that come right to you house to work with you and the dog on it's own territory, and around here they specialize in behavior problems such as agression.

It would be worth your time to call around and see what's available in your area.

Please make sure the rabies vaccination is up to date, and be very careful with him around other people, some states require reporting bites to animal control if someone needs to see a doctor.

Good luck