1 - Yes. But don't forget the Porsche turbo trans. RCR cater for these.
2 - Right
3 - Contact Chris
4 - I think he has several street trannies. Contact him. May not be interested in a one off sale though. Or trans only sale.
5 - Right. Right. From what we are led to believe on here.
6 - Right.
7 - I always think rod shift is more positive, but it gets too complicated with centre shift. There are some excellent cable shift setups out there, usually Jap based shifters. Sill rod shift is classic and simple, so go with that.
8 - I think Fran (RCR) sources the occasional tranny for customers, but talk to your supplier.
Since you asked, if I were you, I would go for a 930 trans. Best bang for buck. Or a G50/52. Both will handle the torque as well as, or better than, an RBT. And at a fraction of the cost. ZFQ would be next choice, if you want to be a guinea pig. No doubt they will be fine but they have not really been proven yet.
All the above IMHO of course.
Cheers