Dad refuses to let us take him back to the shelter, saying that no one else will adopt him once they find out what's wrong with him and that he's a puppy. The shelter site says they only put animals down due to disease/behavior problems, and his issues might be considered such. I tell mum we should take him back, as much as it breaks my heart, and mum says that it won't happen because dad insists this is just a puppy thing and isn't fair to Spector.
I'm 99% certain the shelter is not going to consider euthanasia for his "behavioral problems", because the thing is he actually doesn't have any. Your dad is right, these are just
normal high energy puppy behaviors. Spector is not doing anything that every single one of my dogs hasn't done when in the puppy stage. The difference between your situation and mine is that I am prepared to appropriately handle these behaviors, your family is absolutely not prepared to do so. Nothing your dad has done or is doing will improve Spector's behavior.
Instead, the way he (and everyone) is going about things is making Spector worse.
This is not a condemnation of you or your family, this is just plain and simple fact. While I understand that you believe the shelter misled you about his age, it doesn't change the fact that once the true/healthy Spector was revealed he is plain and simply the wrong dog for your home.
Two years from now he will still be the wrong dog for your home. Even though he will be an adult his energy will not suddenly disappear, but he'll also have two years of little socialization, no appropriate training, lack of meaningful exercise, hitting, smacking, yelling and manhandling under his belt. If Spector remains in your home, by the time he reaches adulthood he will be a dog with serious behavioral problems and every single rescue you contact will consider euthanasia.