My scary dog story. When I was little (9 years old or so)we had a German Shepard. Got him as a puppy. Stormy was wonderful and loving. We had him successfully obedienced trained. It was really an Ozzie and Harriet kind of story. Stormy would actually wait for me outside my elementary school and walk me home.
When he was about 3 he started to get aggressive. Wanted to eat small dogs. Bottom line was that my parents were appropriately very concerned. After all the attempts at other solutions, my parents finally donated Stormy to the Canine Corps. As a child I somehow took comfort in knowing that Stormy was well taken care of by a soldier...and was doing his part for our country!!
Anyway, I do feel for you and hope you can find a happy solution for Stew! Good luck!