I wouldn't be able to return a pup either.
A significant difference in length between front and back legs is not common in Yorkies. Minor differences that throw off the topline (line of the back, from shoulders to tail) are common. The ideal or standard is that the topline is straight, a perfect horizontal line.
I'm no expert by any means, but my only concern would be that the difference in leg length may make the pup more susceptible to back/spinal problems. More stress may be put on the back. I'm not sure if there is anything you could do about it other than be aware if he ever shows any signs of back distress. Do you have a picture of Wally that you can share here? A side view to show the difference in his legs?
I am not familiar with split tongues. Did your pups come from the same breeder?