If this was in my flock, I would keep the RIR and cull the more aggressive cockerel. You can take him off the roost at night and do the deed. Enjoy him as dinner. That will let you see how the other cockerel would behave if he is the only male around. Any aggression from him and he goes too. It's never to late to cull for peace of the flock, and safety of the humans. I've had much success using the broomstick method to cull. I've also put a .22 in the back of the head, for one that was very sick. Good luck to youI have the chickens in an area enclosed by a poultry fence, far away from the one neighbor that we do have and far away and inaccessible from visitors or delivery people. My children are far too young to even be able to get outside by themselves, let alone into the chicken area. So these aren't problems now or in the next few years.
The roosters spurs have not come in yet, they are just slightly growing. It will probably be months before they can do real damage.
Considering the above and that I'm a tall large young man, I think there is room now, if ever, to either test things out or to train the roosters who is boss, if that's even possible. This week going to wear some thick jeans and longsleeve and safety glasses and go into the pen and pick up and carry some hens, and see what happens. I hope the rooster eventually figures out he is not getting his way and if he tries to do anything physical he will get smacked away. They are my hens and not his, and he will learn that. If I do this near every day for a few weeks I hope he is smart enough to get with the program instead of repeating his failing behavior. If he doesn't improve then he's being removed.
BTW an issue with culling him I have is that there is just no way this rooster will let me pick him up. If I have to kill him, do I shoot him with a small gauge shotgun? Any advice?