Man I had to read that thing like 3 times I am so high. It's gonna be hard to get all the answers to your questions because there are so many, so let me say on the onset that your whole setup sounds great for a beginner so even if you just do what you outlined you'll do good.

For the nute formula I would go to the GH website and use their formula. I always use manufacturer's recipe.
I don't like rockwool, I think it is nothing but problems and costly overall. I would use hydroton in net cups.
Size of net cups depends on what size plant you want to grow. I personally would configure 5 plants in 6" netpots in bloom hoping to get 4 to harvest.
Beyond that its a matter of preference as to method. I don't like flood tables for instance. I'm more of a DWC or Aero/hydro.