If he is good with family, and not randomly aggressive, he can be rehomed, but it will take work. He is very handsome. Behaviorists, in my opinion are useless for the most part. If my dog was treated like that by a trainer, he'd bite him, too. It's not uncommon for a GSD to react to poor and unfair handling by a stranger with aggression. If the breeder can help with rehoming, I'd go that route.
It sounds to me like the OP has been getting bad advice from the people she's sought for help. Does anyone have a trainer recommendation in her area, so she can at least get the dog evaluated competently?
And to the OP, plenty of trainers will opt for euthanasia because they don't know what they are doing and it is easier for them. Don't go that route yet, at least give the dog a chance and get another eval.