Not having luck with Ducks! ***PICS ADDED***

[Lanissa86]

Ok, here are some pictures of Bob. Although I might have to change his name to Bobette! Looking at Ideals Buff ducks the girl is the one with the purple colored beak...hmm...

 

[DuckLady]

Bob is adorable! Based on your answers to the questions and the pic, I recommend the following (as well as the brewers yeast additive! Good Call Katy!)

Try making him a shoe for his foot. If his foot is curled it will be uncomfortable for him to walk.
Get a plastic butter dish lid, an old credit card, something stiff. Put his foot on it spread out and trace around it. Cut it out and tape his foot on it in normal position using paper medical tape. Wrap with a piece of Vet Wrap to give the shoe some traction. Leave it on for a few days and see how he goes.
If you can't get the brewers yeast right away, you can give avian vitamins or polyvisol 3 or 4 drops a day for a week.

Edited to add that the bill color might not mean much as far as the sex. The Buff Duck in my avatar was a male.