How long has he been eating egg layer pellets?
Looks like more like a White Plymouth Rock cockerel to me. This is a dual purpose breed and at maturity he will be a large rooster.
You are doing him no favors feeding him layer pellets mixed with corn at his age.
I would get some chick starter or an all flock feed (18-20% protein). Feed him free choice (make food available for him during waking hours). A very small amount of scratch or a small piece of veg can be given once a day as a treat.
I would also get some Poultry Cell and give him a direct dose at 1 cc per 3 pounds of weight once a day. Give the vitamins 2-3 times a week.
His leg issue may be genetic, disease like Marek's, etc. hard to know, but they may also be due to too much calcium (layer feed), too little protein and a limited diet.
Keep him outside on the ground and off slippery floors.