I too have a black Porsche.
You have a good set of products. 3M SMR is good stuff, but technique in using it is EXTREMELY important. If you have swirls it isn't taking care of, get some 3M finesse-it II Finishing compound and use it first. If you use it improperly it will leave a terrible haze. If you use it properly it will bring back a pretty good, but not perfect gloss. Now use the same technique that brought back the gloss with FI-II, with the SMR - i.e., keep workin' it! Once this is done, optionally polish or glaze, then wax. Try Meguiar's Gold Class Liquid (best gloss) or their #26 Hi_tech yellow - I think both are better than their pure carnauba. And if you want a REAL treat, top it all off wth some Pinnacle Souveran.
I have used this exact recipe several times now on a few different cars (check out
Back to Black ) and I am very happy with it. By the way, if you have a chance to swap out your 3M SMR for some Meguiar's Swirl remover 2.0, I recommend it highly. I think it might be SLIGHTLY less aggressive from an abrasives standpoint, but it is also much easier to use and leaves a beautiful finish when done.
lastly, if you can feel the scratch with your fingernail it is prtty deep. You can significantly reduce its appearance though, with another "miracle" product - meguiar's "Scratch-X". Very good stuff - apply with foam pad and one finger, rub back and forth with firm pressure in the direction of the scratch (not across it). Rub vigorously. As it starts to dry out, lighten your pressure and keep going until it is almost all gone.