The first red flag to me is he’s gotten the big head by having been allowed to have free reign of your place at this young age. A cockerel ought, in my experience, to earn this privilege, before being let out to roam freely, or readily taking the hens as his own. In situations where there’s an established cock to keep him in line, that’s different, but eventually he’s strong enough to overtake the hens. I like to let the older hens raise them, until they’re getting to maturity, then, if no older cock around, I keep him separated until I know I’ve got his respect first. I prefer to do this with a small group, rather than a lone cockerel. Only then does he get his own hens, if he is well behaved.
How long has he had this freedom? If he’s had it all his life, I think it would be best to make a decision to not allow this to happen to anyone, yourselves included.
He may make a fine meal for someone, but alive, he’s already taking over, this was no defense, but offensively he attacked.
As you said, your attempts are not working.