Well, it definitely sounds like the right steps are being taken, 757. My advice is to keep it up. If there is any place you can take him where he can run free, do that. Take a tennis ball or something else that you can throw and he can chase. Running is a great way to wear out a dog.

The time to work on his aggression is when he's tired. Don't back down from him. He needs to learn that you (and your family) are the boss. He's been taught that he's the king. If it takes a muzzle to keep from getting bit, so be it, use a muzzle. Avoid drugging the dog. Keep it up, you're doing a good thing by trying to help this dog!
BTW, here are my baby killers...(Rottweilers)
Boomer -
Harley -