My neighbor has a Yorkie that is 16 lbs and she looks like she is all yorkie like yours does!!
Wookie

is currently 8 lbs and the vet says between 7-8 is good for his size frame. He was up to 10 lbs (after spending Christmas at grandmas who's motto is "He is at grandmas, he can eat whatever he wants!") but that was a little too much for his body. (Not good for the luxating patella). But from what I understand it varies from yorkie to yorkie!! You just got more to love than others!! More to cuddle!! Lucky you!