The chemical guys microfibres are good and will get out some heavy stuff.
If your having issues getting the rupes polish off you might be using too much/ not working it in long enough. It should be pretty clear by the time you've finished polishing and that's when its ready to buff off. Otherwise maybe spraying on some quick detailed will help when buffing off. I do find cloths that are too thick/ soft don't buff off polish well, they're great for wax but for polish I use a good quality all purpose microfibre as they're a good balance between soft yet firm enough to remove easily.
If would go easy on that door and start light then work up slowly if it needs more.
I would maybe try some 2000 on that scratch if you can't get it out with just polishing, 2000 then 2500 then a good polishing should come up nice. Maybe watch a couple of YouTube demo's on wetsanding as you can learn a lot from them.