Sounds like you could have done a pear sauce instead!
I don't know much about back sweetening with juice. First you would ferment apple juice dry, and then stabilize it, usually with chemicals, though age does help, too. Then you would add juice, but I don't know how much it takes. Apple cider is sometimes so mild, and other fruits don't do so well fermenting. I've seen it done that way with pear, cherry, black current, pomegranate, and probably some others.