You can't apply SG on top of #7.
Well, you could, but it'd be pointless.
I'd just skip it and do AIO and SG.
If you've got swirls, use an abrasive polish first.
What can I use for glaze? I did my car couple weeks ago with AIO+SG (2x)+S100. I am happy with the result but I think that I can bring the darker, better shine, watery look to my black paint. It is an 04 E320. What can I add to the above steps?
AIO/SG are great products but they aren't the best products to make your black paint deep and wet.
I'd just forget about AIO/SG and go with #7 topped with 2 or 3 layers of S100. Try Pinnacle Souveran if you can get it.
Durability won't be as good, though.