The controller action is called after the completedCallback not after $(this).submit(). See the code below. How can i trigger the action before raising the completed callback wi
Maybe your action can return a url var, like ?status=submitted?
Then check in your javascript if that var exists and if so, trigger your completedCallback.
By the way, you should return false in your $(form).submit(function(){return false;}); if you dont want the form to be submitted if flag == true.