This is a hard decision to make. And your case is harder still because there are people around you who disagree with you. And they might carry a lingering resentment over the decision you make.
My advice: Take your poor dog to a vet whom everyone trusts, one who puts animals ahead of profits. Then ask that vet, “What would you do?”
There isn’t a vet in this area who wouldn’t treat to the max. All the vets have bright shiny hospitals and mortgages to meet.