I'm not sure if it's been mentioned, but I would recommend getting an exam at the vet because some dogs tend to be aggressive when something bothers them.. even if it seems like there's no reason for the aggression.
Also, is he getting daily walks? It's crucial for dogs to go out and sniff, pee and whatever they need to do. My dog had some behavioural issues and walking improved it significantly. My one year old Roy also didn't pay much attention to anything on his walks until he turned one. He still doesn't care for treats outside; he just wants to sniff around and go around marking. He was so excited about seeing other people that he didn't care about me and now I can walk off leash with him and he doesn't let me out of his sight. Somethings just change with age.
Like others said, train him daily and be persistent. Don't expect miracles overnight. It might take a couple months but give it sometime and hopefully things will get better
