You should be able polish those scratches out no problem.
Question 2 - No return edge. A little bit of curve on the outside where the plastic bent around (where it would have met the edge) is okay but there should be NO inside lip/return edge whatsoever.
Question 3 - Gloves, unless you add a liner like some do, add minimal bulk, but I would still do any trimming after buying those just to be safe. FWIW my forearms are snug, I can get them on/off but it is a little tight - but that's the look I wanted. Too big and they look boxy to me.