Hmmmm if you love your puppy then that is all that matters! The pup could be purebred and just not meeting the standards of the yorkshire. Sorry, but the pup looks more like a mix to me. Breeders send off for the paperwork using the registrations numbers of the parents. I suppose that they could get those papers for anything and no one would ever know unless a DNA test was done.
I think that if you are spending a lot of $$$$ then I would have a problem with it regardless since he doesn't look like he will meet the standards, but if you got a good deal...then who cares?? Every puppy needs a loving home and you seem like you could sure give that!!!