Let me try and take this one at a time for you.
Your Drake,,,
Put him aside away from the others. Separate him with some chicken wire. I'm going to call this solitary confinement. Let him see the others but not be able to touch them. Next he thinks he is the "man"
You are the "man" and you need to express your dominance. Grab a book take him with you pin him gently between your legs so he can't get away. Bring him a little water and don't do this when it's hot outside. He'll overheat. Lock him comfortabley there for about 15 or 20 minutes a day. Read a paper or whatever. After at least a week maybe 2 he won't mess with them. If he does pin him down again. This is you saying no I am the dominant one.
For the feathers. Here you go...
King Cages Pluck No More
It's for parrots that pluck their feathers but it makes duck and chicken feathers grow back like weeds!! Just spray it on before bed! Then they won't preen it off.
Did I cover all this?