Your Mallard is DEFINITELY a boy. If your KC's head is turning green & both have similar quacks they you definitely have 2 boys. What happened to the KC's leg & how does it get around...
As for hens for your drakes, not a necessity, but a good thing if you want babies. I would try to find them each at least 2-3 hens. They don't have to be the same breed as ducks will cross breed. You only need the same breed if
I think Waddles my Khaki Campbell had a niacin problem forgot the full word, I got him from the feed store came home and saw that his foot was sort of bleeding, and it was swollen. about a week later his foot was gone, now he walks on the lil nub, I call him pegleg at times cause he reminds me of a pirate when he walks, I want to figure out how to make him a little show or little foot thing to put there, seems painful walking on the gravel and brick. He also has problem getting into the swimming pool so I got to corner him to catch him to be able to place him there. Seems like a very happy duck very sweet one, loves his neck rubs lol. I do not think he will be able to fly though
Kahkis get too heavy to fly. Their wings won't get them more than an inch or 2 off the ground. You can try wrapping the little stump leg with vet wrap for cusioning but make sure it gets changed frequently, especially after getting wet. I have seen a couple places thet make "duck shoes" but I think they go OVER the existing foot & probably wouldn't do much good without a foot to hold them on.
Hmm. I think I have some wrap stuff from when I messed up my knee which is the same as vet wrap. I wish I could figure out how to make a foot for him that hooks on around the stump.
That may work. Find the smallest baby shoe you can & attach velcro strips to it to go up around his leg. Just make sure there is soft fabric or felt attached to the back side of the strips to protect his leg. You will probably have to put some kind of packing in the shoe itself too to keep it from slipping around.