A 10 week old cockerel is not sexually mature and would probably also get picked on by your bullies. You'd probably have to wait until he's 6 months or more before he can stand up to an older hen. Even then, roosters will vary. Some will prevent bullying, and others don't get involved in the girl's pecking order.
CGinJCMO gave some good advice. Sometimes it is a particular hen that is the instigator and if she is removed, a new pecking order will be established. Hopefully she will wind up nearer the bottom when she gets reintroduced. I tried this twice with my very aggressive she-male Leghorn (she is mean and mounts other hens :/ ). Helped for about a week, then her old ways returned. I only kept her apart for a week, though, so think it might work better if she is separated longer.
Here is a pic of an EE I hatched. Should be 9 weeks old now. I assumed this one is a cockrel based on feather color. Its comb is really nkt as big as I would have expected though. Any thoughts?
