Great advice!You may want to post on the' duck threads' and get their opinions. Maybe the others bully him when you aren't around. That could be why he reacts when they bump him or come near him. Not pain necessarily but fear of them.
Has he had a chance to swim in bathtub or other? Generally they do better on water because their weight is supported, and any swimming motions may soothe his leg. I'm guessing here, have never been around ducklings.
I have read about ducks that lost a leg and they do quite well on water. Wondering what a experienced avian vet would say. Maybe an amputation would be easier to adjust to and hopefully relieve pain, after recuperation.
Start with a kiddie pool
Welcome from New Orleans, sorry you are having to go through this, however, you have come to the right place as far as compassion and looking for the best answer is concerned. You have gotten some good advice already. If it were me I would post on the duck site for more advice regarding your little friend's leg. IMO his quality of life is most important,( which he seems to have) the Duck peeps will know more about those things than I do. Good luck, I truely hope all works out for your little guy, he is lucky to have you. 

that your little guy is a fighter and does OK!



