I understand how hard it is to walk away from a puppy when you have fallen in love, but my advice would be to consider how LONG that puppy will be an important part of your life;  it is such an emotional and time commitment!  Are you prepared to roll the dice?   
This might seem silly if I said it to a non-Yorkie person, but (as a 2 time Yorkie owner with a new puppy right now) I think that bringing home this special family member is one of the most important decisions you can make for the next 10-15-20ish years.  I do understand that Yorkies are first and foremost 'dogs,' but because of their size and associated care they become very child-like for many of us.   
I applaud anyone who takes the time to ask questions, do research, and approach the decision to adopt.....particularly before the puppy has reached 12+ weeks.....very seriously.     
Best wishes as you struggle with this decision.     |