If this little chick is happy, active, hops perfectly well to food, is able to poop without a problem, and gets along well with its fellow chicks -- and those chicks are accepting and don't bother it -- then why cull it? It has obviously shown that it can survive just fine, and that its flock has accepted it the way it is. As they get older, the other birds may very well "mother" the gimpy chick and be fierce protectors of it. Yes, culling does make sense if the chick is in obvious distress, if it cannot get to food or water, if it just lies in its own feces, if the other birds act aggressively towards it. But your description shows none of this. Your description shows us a little chick who is doing just fine, other than having a gimpy leg.
I guess the real question is, what would you be comfortable doing? Are you willing to put some extra effort in keeping track of this little chick, to ensure its welfare as it grows up? If so, then don't cull. It might not make it to 10, but it should live well with the adaptations it has already shown. But if you've got lots of poultry, with another hatch or batch of chicks on the horizon plus housework, work, kids, etc., and you're not sure you have the energy or time, then the kindest thing would be to cull the little peep.