Rooster with ducks?!?!?

I have a question. I cannot free-range my chickens but they are in a very nice coop with a fairly large yard where they can get out in the sunshine and scratch in the dirt, etc. I have 5 hens and 1 rooster. My rooster, named Goliath, is a Light Brahma and he is the gentlest most awesome rooster ever! There's a problem however.....the hens will NOT stop pecking him! Originally they were pecking his feet and legs. I put some "Pick No More" ointment on them and they stopped. A few weeks later they started pulling out his beautiful tail feathers. All of his long tail feathers are gone and they've started pecking him in the bum! Last week I noticed it was bleeding so I held him down and doused his bum with "Pick No More". For a while they left him alone. This morning when I was doing chores I witnessed the bum pecking again. One hen in particular would NOT leave him alone!!! I'm not sure what to do. I don't want to remove him from the coop. He will be very lonely all by himself plus he would very quickly become predator bait. I have a pen of ducks that adjoin my chicken coop. I have 5 Pekin Hens, 2 Khaki Campbell Hens, and 2 Khaki Campbell Drakes. I was thinking about moving Goliath in with the ducks. What do you think? Will the ducks harm my rooster? Any suggestions/advice would be welcomed!