What if instead you insisted that the dog attend an obedience school.
The dog is insecure/aggressive. Training a dog is to teach him how to behave around various scenarios and to follow orders, it won't change his personality. I mean, you can make changes to a lot of things, the way you talk, where he sleeps, which room he's allowed in, how often he walks out, his toys, etc. These all contribute to addressing his insecurities. It will work, until one day, the routine is not followed, something will happen that wasn't planned, and the dog will fall back on his lower instinct. That day, you'll blame yourself for not properly training him, or for not keeping up the routine, but the real problem is that you invested all this time and emotions into a dog that was aggressive to begin with.