1. Because Tohsaka was just going using Kiryei anyway.
2. Actually this isn't "the grail", I think it says so from the beginning it's a lesser version.
3. Well Archer aka Gilgamesh, isn't exactly "alive". Kiryei is, but I think Archer is just there because he won. Kinda like how Saber exist in /Night.
4. His wife is a clone. Not exactly Ayanami rei but....yeah same scenario.
5. Uh....don't remember that, but the romance is heavily implied.