Rescued Muscovy duckling health & chicken integration

I took in a rescued Muscovy duckling and am in need of some help to figure out if I am doing the right thing with its care. Lots of questions, sorry, that web searches haven't really addressed.

I do not know the age or sex. It's old enough that the wings have just started to get pin feathers. Long tail makes me think its a drake(?).

He/she wasn't able to stand/walk a week ago with toes that twist inwards but now his strength is building and he can sprint uphill about 30-40 feet before getting tired and plopping down to rest. Still sits on his hocks more than I think is healthy tho. Any suggestions?

I'm feeding Purina Layena crumbles and adding in brewer's yeast. I've heard the extra niacin could possibly help his feet. Is the Layena ok to feed? Should I switch to something different?

I have a small flock of mostly older chickens, and a roo. At night they are cooped, in the morning they stay in their run, and from noon to sundown they free-range over to the house. Probably covering 2 acres or so.

If this Muscovy turns out to be male, is it wise to keep him in the coop/run with the geriatric chickens? Will his caruncles be pecked bloody? Should I create a separate duck coop? Could they still free range together? I'm worried if he's male of the whole mating issue...

Last question on the coop situation. I use Sweet PDZ on the floor of the chicken coop for easy sanitary cleanup, and the run is dirt. Would this be appropriate if the duck is kept in there with the chickens?

Thank you!

Young ducks shouldn't be getting layena as its formulated for laying hens that need more calcium.

If the duckling turns out to be male you definitely need to worry about mating, especially with no other ducks around. Otherwise they should be able to stay together, though I would recommend another duck to keep it company.

Thank you for responding. I've been feeding Layena because of a few reasons, the biggest of which is I don't know what else to feed.

He had been on Game Bird chow prior to me getting him, and I'm paranoid with his foot issues of him getting angel wing on top of it. So far, no evidence of that.

Also, he's an older duckling - older than I think Flock Raiser is supposed to be fed. So,.. I'm kind of at a loss as to what to feed at this point.