I have 21 hens and 2 roosters - the Silver Gray Dorking, Duke, is HUGE and definitely the alpha of the flock. I got all of them as day old chicks.
As a little peep, Duke was a sweetheart. He would climb up in my lap and sleep, follow me around, and never minded being picked up. He began crowing at 6 weeks and VERY quickly outgrew the others. He started becoming protective of the girls pretty early - and less affectionate towards me. Which I accepted - I appreciated his role and that he took it so seriously. At about 4 months old, I was cleaning out the coop and it REALLY REALLY upset him for some reason. I clean it every week, but this time, he stood at my feet bawkiing and clucking VERY loudly. All of a sudden, he came at me sideways - and before he knew what happened, I snatched him up and tucked him under my arm. He was NOT happy. But I had Rooster Red's page and he suggested this method - and it worked! I carried Duke around while I cleaned for about 5 minutes. When I put him down, he was extremely humble. And he has not come at me or fussed at me like that since.
Make sure he knows YOU are the alpha. And I agree that if he doesn't "get it" - either make him stew or find him another home.
Penny