In addition to finding another vet, dump the Petsmart training classes. They’re great for most pet dogs without issues, but for a dog like this you need a good trainer that’s very experienced with fearfulness and German Shepherds in particular.
a 3 year old dog that’s fearful will never be not fearful, but a good, experienced trainer will help you handle your dog so their fears are lessened and issues are managed much easier. Your dog will relax a little when he realizes you’ll take care of problems and he doesn’t have to worry about it.
