I want to thank everyone for their input and give a little update.
I decided to separate Little Two with 2 of the other ducklings. I brought them into the house and kept them in a kiddie pool. Little Two I have kept hobbled.
I have brought them all out to the run 3 times a day for part of an hour to be with mom and the rest of the flock and have let them be with mom overnight.
Just now they are all out in the run together and since Little Two's hobble was falling off I decided to take it off and see how he was doing.
I am amazed at the progress! He's running around the run, both feet are staying together instead of one splaying out to the side. He still has just a bit of a limp, but overall I'm seeing great progress. I think I will continue what I am doing a few more days before I let set him free of his hobbles for good.
Overall I'm very pleased with his progress.