Seems like their are different ways to deal with cockerels. Personally, I don't have to time or patience to deal with aggressive roosters. I simply eat them.
I think the best thing you can do with roosters is try to avoid bad circumstances before it actually happens. Once it does, it'll be hard to break.
When I have a batch of chicks, I treat everyone the same. I give them treats, carry them, and allow them to get close to me (peck at my shoe, follow me, etc). However, once I see the cockerels display their rooster traits, I completely change the way I behave around them. I no longer hand feed them, nor do I allow them to get close to me. If they do, I simply back them away with my foot. I don't go as far as to chase them when they crow or when they mate in front of me, since they rarely do and when they do, its usually not close to me.
Don't try and actually hurt the rooster, this will only cause him to not only lose his trust on you, but see you as a possible threat, making the whole matter worst. I had to learn this the hard way, intimidation rarely works, and if it does, it only causes the rooster to be scared of you. Scared roosters don't cooperate and make life hell.
Roosters are great for many reason, but one big drawback is their tendency to be overprotective. Your cockerel is still young, not fully mature yet. I would definitely keep and eye of him. I would back him off if he gets close, perhaps even chase him a bit. Again don't hurt him, just let him know not to get close. I believe when your cockerel grabs your pullets by their neck feathers, he is trying to mate with them. I see this same behavior with young cockerels and young pullets who have no idea whats going on. Over time your cockerel will learn to attract mates properly.
