I'm not sure if he is from a puppy mill but the below link has some excellent advice. Not mention, I'm sure there will be someone on here that can also give you advice.
http://www.yorkietalk.com/forums/gen...nt-advice.html
I rescued a yorkie from a backyard breeder and this link help me tremendously. The best advice I can give is to not force it. Let him come to you in his own time. You have to gain his trust because you don't know what his background is. Assuming he has a clean bill of health, be patient and very loving towards him.
Gaining his trust should be your priority right now. Hopefully he will come around. Just remember that it has to be in HIS time and not yours. Whatever you do, do not try to exert any force in trying to establish who is the pack leader. You first have to get him to stop biting you. He is definitely very afraid.