So glad for Donald and you!! Never give up on a little one with a disabilty if s/he has a will to survive.
I have a pekin drake with a deformed bill from a fight with a raccoon that killed his brood mate. His bill isn't so bad as Donald's. He can't eat greens out of a bowl so I hand feed him. Peas he eats from a deep tapered plastic cup. Regular duck pellets and ducky soup he can manage from a deep dish. He's smaller/thinner than my other pekin drakes but he is very happy and active. He is closely bonded with a muscovy drake and so well practiced at climbing and jumping which the other pekins are reluctant to do.
Do you have to use a deep feeder for Donald?