Sounds cliched, but watch Caesar Milan.
Just some simple voice techniques can and will be able help.
I would t recommend letting off the leash until he feels safe with you, not protective of you which sounds like his behavior, toward other dogs/people.
Also using a small empty soft drink bottle filled half way with rocks helps as a tool to discipline.
Hope this helps.
I have to agree with watching Ceasar Milan, he is fantastic. I know the show seems a bit corny, but I agree with everything he is about. He uses simple techniques that make sense. maybe google him or watch some on youtube.