Give us a picture of the tail. (I'm not able to tell about the blackness or wrinkling without seeing it...dab some neosporin on any cuts he has...send a pic!)
House him with the females for breeding only, when you think he is finished breeding remove him and house him by himself.
Make sure the temps are around 92 for him to eat right.
Yes, some females can be more abusive to the male than the male is to the females. Those cuts on his tail are from the female.
IF HE CONTINUES TO GET MORE BEAT UP YOU SHOULD REMOVE HIM.