Culling just means removing them from the flock, how you do it, is up to you. My point is that adult intact males often cannot live together in a flock. The hormones drives them to try and be the top bird, and they will fight sometimes once and sort it out, sometimes often, and sometimes to death. That is a fact of rooster behavior. It is not pretty, as you have begun to notice, and it will most likely get worse.
Somehow, your decision depending on what you can tolerate, you will need to separate most of these birds away from each other. Sometimes even a fence is not enough, I have heard stories where they fight through the fence.
Personally, I don't like that much violence.