between the ages of 7 and 12 weeks is when the puppy does the most amount of BONDING with you, please dont waste this period by being focused on the negatives.
You said that you know that 5 weeks was too young, but that is a different story, Im sorry to be the one to break it too you, but its the same story, the entire reason your puppy is so bitey, is because it missed 30% of its life, that it should have spent with its litter mates, to learn bite inhibition. This means that your 7 weeks old puppy, is 30% less developed than an 8 week old who is only just leaving his litter mates. I got my puppy at 7 weeks and worried about her biting a lot.
you now have to teach your puppy that bitting is not ok, or if you dont mind him bitting, that he must be gentle on soft human skin. I did the latter, because my dog likes it when I put my hand in her mouth, when she would bite gentle, I would tell her good girl and give her strokes, when she bite too hard, I would remove my hand and say "AHH AHH!", if she got rouwdy, I would tell her no and leave the room. i believe soft biting is the easiest and least frustrating way of teaching your puppy, because they dont have hands like we do, they do everything with their mouths, imagine how frustrating it would be for you to spend the whole day with your arms by your side, and then everytime you tried to use your hands, someone told you off?
if your puppy is an alpha, he will challenge you between the age of 14 and 18 weeks, there is no way of knowing right now if he is or is not an alpha. But pinning your puppy to the ground is not a good way of ascerting your dominance right now, its a good way to break the bond between you and your puppy.
Maya, GSD Bitch, Born 30/08/2012..... complete lapdog.