2 – Wired to 1 ohm, that amp will be more than sufficient. It's good quality and in all of my testing it can attain it's rated wattage without clipping.

3 – You probably don;t need 200 ft. of speaker wire. 100 will probably be enough. If you use a harness adapter for the head unit, you may not need more than a few feet.

4 – The box should be good. Those subs work pretty well in a smaller, high tuned enclosure.

5 – It looks like you have the bulk of the necessities for the amp install. You'll probably need a few ods and ends, screws and such.

6 – From the looks of it, you'll have to hook the mids and highs to the head unit. You would need a seperate, 4 channel amp to power them any other way.

7 – Yes, you can wire 2 dual 4 ohm subs to a one ohm load. Wire the coils and the subs together in parallel. Use option 1 from this link.

All in all. The only thing that I would change in the set up would be the head unit. The legacy units aren't very good quality. They have a tendency of crapping out after a few months. In my opinion, you would be much happier with a different unit. Look for a Clarion, Alpine, or Eclipse that fits your price range.