Seems like an OK food except for the corn gluten meal and the chicken flavor (???).
What you describe sounds like a hungry pup. Pet him with a flat hand over his rib cage. If it is too bony or you see the comb on his spine he needs more food. Puppies should be trim but not too thin. Since he is biting his legs I would take him to the vet to check for Pano, common in young males and you can also ask about his weight. Don't let yourself be talked into the crummy diets that vets sometimes prescribe like Science Diet or Purina. (they sponsor vet programs). Forget what the package says; every dog is different in metabolism and activities.
To know if you are doing things right, you should be willing to trade places with your dog.