I can't tell you what to do with your chickens, but I will share our experience with you and maybe that will help.
When we first purchased chicks we bought nine, and they were all getting along wonderfully in the brooder box. One morning, out of the blue, one of them went crazy and began attacking all of the other chicks. We separated out the wounded ones, and treated them. However, one by one she was taking them down. They had bleeding backsides, plucked feathers, bleeding heads, and near their wings as well. She seemed calm among the chicks who were the same breed as her, so we placed her, and the two like her, in their own separate box. By the next day she had attacked them as well. We removed her completely and she spent the entire time she was alone crying--she wanted to be with all of the others, but every time we tried to place her back with them she would attack them again. Meanwhile, the others were beginning to peck at each other because the wounds were curious to them. We had a peck-fest going on, and it was difficult to stop.
Ultimately we put her down. For the good of the other eight I had to eliminate her. We tried everything suggested for calming an aggressive chick--different lighting, less heat, salt in the water, blu-kote, etc. Nothing worked. In the end we had to decide if she was a detriment to the health of our other chicks, and she was. We had one that, while being treated, went into shock and would have died without fast thinking on our part. Since we made the decision everyone else has gotten along wonderfully. They now happily hang out together in the coop, and I have not had any other issues with aggression, etc.
Sometimes you get one that can't be taught. When that happens you have to decide what is best for the flock as a whole. I would suggest that you google how to deal with aggression in roosters, and try what you can (maybe you already have). If nothing is working, then I would consider eliminating or rehoming him.
So sorry you are in this situation. I know it's frustrating and perplexing. Good luck with your decision.