Honestly.. you may just have to manage that behavior. Not saying it's not fixable but realize that coming from a rescue and 2 homes will have taken it's toll.
I would suggest at the moment not bringing him out when there are people around. He is ok to just be in another room relaxing and chewing on a bone. I would also DEFNIITELY get him to a trainer and have him evaluated. They would be able to help you figure out the ebst course of action.
Commander Charly Titan (GSD)-15 Jan 2010