Are you anywhere near a veterinary school? When desperate, I’ve gone to Tufts in the Boston area.
Good that you’re trying to find a stable vet, but remember that vets that don’t know your dog won’t have a history to rely on for comparison with his current condition.
And beware with large dogs. A vet killed my Irish Wolfhound because he’d never treated one so large and was too scared of it. Gave it too much sedative and wolfhounds have a different bone/muscle ratio than other dogs. He should have called me as he could have worked on the dog, who was pain insensitive, without any sedative.
We have one of the best a couple hours away. If I get no help from my clinic, I will go there Wednesday.