From what you write you are not dealing with a breeder. What you are dealing with is more than likely a back yard breeder...maybe even a broker. Personally, I would report it.
If you bring this pup back (which I doubt they will take back), this baby may be destroyed (not humanely) if they are out to make a profit. Since the puppy is yours now, I would take responsibilty if they are not stepping up to the plate.
I actually would be getting a second opinion. I do not know how a vet can say that the dog will go from 1-4. Did the vet mention anything about long term care and prognosis?
If there is blood circulation problem that he/she can detect, did they mention if this had anything to do with the murmur?