Meg's #4 is a rotary only product.
It probably wouldn't hurt to use #9 with a DA but from my experience it's usually pointless. It was designed for very fine polishing with a rotary and has hardly any cut at all with a DA.
If you got most of what you want with one round of Fine Cut, you could try a second round. But I'm assuming it was your test spot and you want more effect in one round.
The Scratch 2.0 <span style="font-style: italic">should </span>be stronger than the Fine Cut Cleaner. Different finishes respond differently so that isn't an absolute. But if you haven't tried the ScratchX 2.0 with the orange pad and the techniques from the vids, you should.
The next step up in strength in Meg's consumer line is their Ultimate Compound, which is actually stronger than most products in their professional Mirror Glaze line.
If that doesn't take care of it, it may be time to start thinking about a process with more power than a DA with Griot's foam polishing pad can dish out.
Never sprung for a carfax, but I think I'm the third owner of my JH, second if you don't count the dealer the first owner traded it in to. I brought it home in '84.
pc