x2 the pecking back.
Don't let him attack you. Peck him back, then chase him around till his hackle feathers are plastered to his neck. When he gives up trying to fight back, you've asserted dominance.
That's how it works between roosters. If you let him fight with you, you're letting him know that who's in charge is still up in the air. Chase him around, peck him back, and don't give it a rest until he stays out of your space.
Keep your eyes on him at all times. If he comes into your space, shuffle towards him or stomp at him. He may come at you but peck him back. Eventually, he should stay out of your space.
If he doesn't, invite him to dinner.
I've heard that aggressiveness can be passed on to offspring (don't know if it is true) so I would be hesitant to use him for breeding.