I'm interested to learn what you find out and am following along too.
You've probably already tried but you could reach out to other trainers and veterinarians.
About 15 years ago we adopted a German Shepherd. It's a very long story and I'll spare the details but we were her 3rd owners. We were told by one trainer to put her down that she would never fit into any family. It took close to a month before I could even get any trainer to talk to me about her.
Finally I found a trainer who lived 2 hours away. He specialized in difficult dog behaviors (dogs that bit). So we took her to him and he evaluated her. We ended up working with him and 2 other trainers to bring her safely into our home. In the end she became a well behaved, precious, loving family member.
I don't remember the trainers name. I've tried googling him with no success.
I wish you the best finding an excellent qualified person to help.
#AnimalBehavior,TrainingandEnrichment