Providing plenty of places for hens to get away from him might help (raised perches to sit on, objects they can run on all sides of to get out of sight, and so forth.)
A divided pen might help. The male could live in one side, the females in the other side, and they can socialize through the wire mesh divider. That could let the females have a chance to finish growing up. It is not a long-term solution, just a way to manage the situation until they are more grown up.
Depending on how the cockerel is acting, getting beaten up by older hens might be exactly the right thing for him. Of course you don't want serious injuries, but he might benefit from learning how to be submissive to bossy older hens.
Definitely consider whether to have a rooster at all, and whether to have this one in particular. Sometimes the best solution is no rooster or a different rooster, and other times the best solution is to work with the one you have.
Butchering the cockerel is always one option, but because it is permanent, I would definitely try other ideas first.