I have tried to understand rooster behavior. I think your rooster's behavior is normal. If I can be so bold as to describe what I think he is thinking. He thinks you are either going to mate his hens or hurt his hens. If he decides you are going to mate with them he is going to knock you off their back when you mount. If he decides you are going to hurt them he will fight you to his death or yours. If you move slowly and his hens stop calling for help he might not attack. You must be (act like) human not rooster.