I would think of maggie first also. Especially at her age. I think if you wait, something might happen.And this is alot of stress on Maggie. They are trained people and will get him the help he needs to get another "forever home". I would be thinking of Maggie. He is showing signs already of aggression towards you. They will get him a skilled trainer when he is returned. Its not like this dog is chihuahua- this is a dane- and totally capable to causing someone or Maggie serious injury.