Mister formula ford, I think you need to do some searching and reading before making another thread. R3Vlimited, and E30tech are your new bibles.
Your goals cannot be dual purpose. You build a motor for either or, NA or FI. Make a choice.
1. Get an eta crank, cheaper, and just as robust.
3. No, they can go higher.
4. M50 swap. Newer, faster, reliable and cheaper. You can't honestly tell me an M50 swap is 10 times more expensive than an M20 swap, especially an M20 that's been rebuilt.