the Ian Dunbar bite proofing advice is first class. If pup bites clothing and tugs, put your hand over the muzzle and press gently inwards opening the mouth and disengage the clothing. If you have extremely short nails and can do it gently, as the pup gets hold of your fingers tickle the roof of his mouth and say "gently" pup should open his mouth and back off. I would also stop the encouraging the rough play that leads to biting and certainly don't initiate it yourself, tempting and fun though it is