1) BEC's can run sub 1000#'s. CEC's for the road seem to run 1300-1400#'s Subtract xx#'s for fuel and engine to get where you want.
2) a 1500# car 9wet with driver) takes only 140HP to get sub 5 second 0-60 times See http://www.060calculator.com/
3) Don't know; don't care. It wouldn't be a streetable sevenesque car here in Illinois.
4) Again, don't know. Highly dependent on Cd and frontal area. Cd of a typical Seven is around .7 to .8. Any changes you suggest only make small changes. 200MPH is quite a stretch for our builds. As you need more HP, the frontal area will undoubetly increase. See http://www.wallaceracing.com/Calculate%20HP%20For%20Speed.php
Might want to search out the supercharged Stalkers.
5) Oh wait. There is no #5
6) Don't know unless we all get together and race. Theoretically, my car will get to 174MPH at red line. If I only had enough power (and cajones) to get there. If I ever get there (not), I'll just tweak up the RPM limiter a bit.
7) been discussed - search the site.
Based on your questions, what you are looking for , is not in the spirit of Sevenesque cars. The Seven gets its advantage from being quick, not fast. That is not meant to discourage you from dreaming.
Moderators, I believe this post belongs in "In theory it could work...."