I do not have much advice for you, but I can tell you that I have spoiled every Yorkie that I have ever had and it never amounted to them having aggression issues. We do have a yorkie that I do believe was the result of poor breeding and he has had alot of physcological issues. We have come along way for sure. I have worked with him for 2 years and he is finally a well rounded dog most of the time
Good luck!