I don’t know what I’d do if I had to give up my dogs, let alone so quickly like that. I am sorry for your heartbreaking situation. I bet there is a rescue out there that will take him. Keep looking. When we last needed to add a dog and found that the Wisconsin Doberman Rescue had no dogs available, we easily found the Illinois Doberman Rescue and had a dog within 2 weeks. The internet made it so easy to find a doberman who needed a new home. That rescue takes in dogs with all kinds of special needs, physical or behavioral. They even take non-dobermans and cats. Perhaps the trainer you mentioned will come up with a solution for you. I sure hope so.
How heart-breaking for you. Please do everything under the sun so euthanization is not an option.