I would separate the ducks from the chickens. Have two separate pens.
Drakes don't mix with female chickens. Drakes can really damage a hen if he tries to breed it. They aren't made the same.
I have 2 drakes and 7 hens. Plenty of fertile eggs. I would get at least 2 hens if you get a drake.
Yessss Icannot stress this enough DO NOT put drakes in with hens
My two drakes killed three of my hens before I even knew what was happening
I had to make them their own area
But I lost one of my favorite girls a beautiful silver laced wyondotte