I'm happy you took him, and it is working so well for you both! As kickstand said, heavy socialization. Maybe find friends with non aggressive dogs and visit often, teaching him how to behave. If need be, find a trainer to help you both address the right way to learn. good luck!
The wife and I are in the first couple of weeks of a trial for adoption of a rescue dog. I will start a new thread about her, as not to hijack yours