Awww...he's cute. I would watch him and if he can't use his leg them keep him,otherwise if he seems to be in pain take him to a vet to have him PTS.
I would take him off the Care Fresh (I think that's whats in the pictures) and put him on something like dirt or eco-earth/coco fiber.And add a hide.
Feeding him:Try using tweezers and hold the cricket in front of him or giving him small crickets,also provide food for the crickets in the tank.
Meal worms should be fine to feed him,assuming he's big enough.
Have you identified him?