You are in a tough spot. It's very hard to deal with a dog like this, even if you know what you are doing. I would be looking for a good trainer that has dealt with dogs with behavior problems before - I'm not a fan of behaviorists. I obviously haven't seen your dog in action, but suspect this is going to be a case of managing his issues and not fixing them.
As for the car, a crate is definitely in order and possibly keeping it covered so he can't see out might help.
Elaine and the herd