My heartfelt sympathies for the poor poor puppy that had the misfortune to end up with such callous owners. I hope he finds the loving home that he deserves with owners that are willing to stick with him through the good and the bad.
And perhaps your family should rethink the concept of adopting animals. A robot dog may be more up your alley.
Pets are not "things" you throw away b/c when they become disabled, sick, or a tiresome inconvenience.
This dog did not ask to be adopted, he did not ask to be mistreated, and now that he is sick by virtue of that mistreatment - he is an inconvenience being thrown away b/c he is in the way.
People that treat animals as disposable "things" have no business having pets.