Let me give you three links that give what think is good information and some different opinions on this. I think they will help you.
Breeders managing roosters
https://www.backyardchickens.com/forum/viewtopic.php?id=250327
Number of roosters thread
https://www.backyardchickens.com/forum/viewtopic.php?id=219443
Managing multiple roosters
https://www.backyardchickens.com/forum/viewtopic.php?id=229968
We all have different goals and circumstances, so one answer is not going to be right for all of us. There are potential problems in keeping roosters, potential, not guaranteed. Many of us keep multiple roosters with out flocks and don't have big problems, but there are some that do have problems. My normal advice is to keep as few roosters as you can and still meet your goals.
There is no magic number that will guarantee you that you will never have a problem. Some people keep three roosters with two hens and things are great. Some keep one rooster with 18 or 20 hens and have problems. Many things go into it. In my opinion, the individual personality of the roosters and hens is the most important, but other things, like how much room they have, are also important. These comments cover everything from roosters fighting to barebacked hens. There is no magic number, but I agree the more roosters you have, the more likely it is that you will have a problem.
I can't tell you what I would do in your circumstances. My goals are different. I personally would not put up with a rooster that attacks any human, especially if there are kids around. I'm not criticizing you, just pointing out some differences. There is a possibility the Buff Orp will mature properly. Maybe not. Their personalities can change, either for the worse or for the better, when they become the dominant rooster or as they mature. There is obvioously no telling how your BR will turn out.
My young ones avoid the older ones too. I don't have any adults that go out of their way to search out and destroy the young ones (some flocks have those chickens), but the adults remind them very clearly that it is bad manners for chickens lower in the pecking order to share space with their social betters. The young ones wisely try to avoid the adults.
Good luck! It is not always an easy decision.
Breeders managing roosters
https://www.backyardchickens.com/forum/viewtopic.php?id=250327
Number of roosters thread
https://www.backyardchickens.com/forum/viewtopic.php?id=219443
Managing multiple roosters
https://www.backyardchickens.com/forum/viewtopic.php?id=229968
We all have different goals and circumstances, so one answer is not going to be right for all of us. There are potential problems in keeping roosters, potential, not guaranteed. Many of us keep multiple roosters with out flocks and don't have big problems, but there are some that do have problems. My normal advice is to keep as few roosters as you can and still meet your goals.
There is no magic number that will guarantee you that you will never have a problem. Some people keep three roosters with two hens and things are great. Some keep one rooster with 18 or 20 hens and have problems. Many things go into it. In my opinion, the individual personality of the roosters and hens is the most important, but other things, like how much room they have, are also important. These comments cover everything from roosters fighting to barebacked hens. There is no magic number, but I agree the more roosters you have, the more likely it is that you will have a problem.
I can't tell you what I would do in your circumstances. My goals are different. I personally would not put up with a rooster that attacks any human, especially if there are kids around. I'm not criticizing you, just pointing out some differences. There is a possibility the Buff Orp will mature properly. Maybe not. Their personalities can change, either for the worse or for the better, when they become the dominant rooster or as they mature. There is obvioously no telling how your BR will turn out.
My young ones avoid the older ones too. I don't have any adults that go out of their way to search out and destroy the young ones (some flocks have those chickens), but the adults remind them very clearly that it is bad manners for chickens lower in the pecking order to share space with their social betters. The young ones wisely try to avoid the adults.
Good luck! It is not always an easy decision.
) by the other rooster. I felt bad, but I didn't want to come out to the house and find him mangled. It seems kind of wrong to have kept the meanie, but this one had a crossed beak and I think a broken foot. He was limping and it was swollen. He was scared of the other rooster so much, he didn't even stand up straight. He walked around with his head all scrunched down. It was disturbing. He also had trouble eating because of the beak. 
