I got 325g aspirin, did some math, and 1/4 tablet in 4 cups of water is the equivalent. My duck with the bummed leg is getting better after resting in a sling for a day. I just gave her aspirin now, so I hope she feels better today! Good news is that she's starting to put pressure on the leg...
With it being swollen that makes it harder to get it back and painful too. You could try making a sling so the leg hangs down that may help.
https://www.backyardchickens.com/articles/leg-foot-and-toe-issues-in-poultry-of-all-ages.68093/ If you scroll down you'll come to the info on slipped...
All I have seen of slipped tendon is the leg won't lay down flat like normal. Have you tried to slip the tendon back in place? The hock looks swollen from here.
How much B complex are you giving and how?
It could be a deformity.
So the leg won't bend straight down in a normal position? and it's at the foot and hock?
I doubt missing the back toe is any kind of problem is the toe on the other foot?