There are yorkies that are very healthy at 2-3lbs. I think it is important that the extra tests are done. I would also recomend a Bile Acid test be done after 20 weeks.
They really do require alot of extra attention and time, making sure that they are eating well and frequently. And watching that they don't get underfoot or sat on. Also when they get sick they can go downhill or dehydrate quicker so it almost always means a precautionary trip to the vet. Just because it is small doesn't mean that it will be unhealthy, but it does mean that there is alot less room for error.
Oh, and AKC is registry to verify the lineage of your dog, it will not tell you that the dogs are healthy or that the breeder is ethical
