advice re:ground connections inside a metal box
I just did that today.  The box's ground screw hole wasn't on a dome, and it was mounted on a metal surface, so I couldn't use it without bottoming out.  Just grounded to the receptacle, which is hard flush against the box, so done.  Switches don't need to be hard flush; they are allowed to ground via the screw threads even if the switch is not hard flush.