I will go with the minority in that I think your dog could be 100% yorkie, but with the red legged gene. I recently met someone from here who's had posted about her pup's hair not growing much and then I met her at the local petsmart and seen her Yorkie in person. Lilly looks a lot like your pup, honestly I think they are redlegged.
Here is a link to an old post on YT about the same thing
http://www.yorkietalk.com/forums/showthread.php?t=16341