Am I very sorry to hear about this.
TODAY I would send the breeder a certified letter. Then immediately go back to Banfield and show them your vet's diagnosis.
You are probably going to have to take this to court if your breeder doesn't cooperate. Do you think that in light of the circumstances your vet would let you make installment payments so that your Teddy could have his surgery?
Rest assured that Teddy will be fine. And your mom knows your heart. This situation was not of your doing.
Here's a hug girl. EVERYTHING will work out to your favor.