Oh I am so, so sorry to hear this, poor Pepper and poor you, all my heartfelt good wishes and positive thoughts are with you.
As many of the others have said, the breeder is morally responsible to help you with this sad situation. I find it hard to believe that the breeders vet didn't pick this up but at the end of the day it is the breeders responsibility to help you in every way possible.
I know that you have Peppers wellbeing to think of more than anything just now but please check this;-
Did the Breeder have Pepper Vet Checked before you brought him home? As this an expected requirement.
I would expect the Breeder to put the money you paid for Pepper towards his treatment.
Keeping fingers and toes crossed for Pepper.