The 1 to 10 ratio is about fertility, nothing else. There is no magic number that will stop roosters from fighting or stop barebacked hens. The rooster to hen ratio is a factor, but there are no guarantees.
Roosters fight for flock dominance and for pecking order. Sometimes they can work out there differences and work as a team protecting the hens. Sometimes they fight to the death. If they are raised in the same flock, such as brothers or as father-son relationships, they are a lot more likely to work out their differences. Having more hens to share, more room, and separate feeders-waterers all improve your odds, but there is no magic number. And there will be fights. It is how hens and roosters establish pecking order and roosters establish flock dominance. They are social animals and that is how nature has worked out for them to get along. It is the severity of the fights that can be a problem.
Some people have just one or two hens with a rooster and don't have barebacked hen problems. Sometimes a rooster with a large choice of hens will pick favorites, and especially if he is larger, has really sharp spurs, and his technique is rough, you can have barebacked hens regardless of the ratio.
In both these cases having more hens to roosters helps your odds of not having these problems. My advice is to keep as few roosters as you can and still meet your goals to reduce your chances of these problems. And if you have to rehome some, do them all at the same time if you can. You are going to change the pecking order, so they will have to sort that out. I think it is better to do it one time instead of dragging that process out. Less chance of injury.
