I used to be a real die-hard Trekkie ... I'll answer your questions:
1) Vulcan was never destroyed. Apparently they included that Romulus was going to be (and was) destroyed. The TV-series and movies never covered any of this. What Unification to see how Spock got there.
2) Spock and Uhura NEVER had anything at all. In TOS (The Original Series) it was Kirk and Uhura who had the first on-screen multiracial kiss. It created quite a stir back in the 60s (think Civil Rights Movement). But other than that, there was never any romance hinted at among the crew members. In the movies, they all became more like family, but never any romantic love was shown. That single kiss between Kirk and Uhura was it.
3) Watch Unification. Vulcans are very long-lived. Think like Wookies from Star Wars, only they don't get that old.
4) No. The crew was formed in piecs. In fact, Chekov was never part of the original crew. I think he joined somewhere in the middle of the series, I can't remember. That's a huge mistake the movies made in the 2nd movie, The Wrath of Khan. Chekov never met Khan when Khan first came aboard the Enterprise when the ship found the SS Botany Bay. It's been talked about that maybe Chekov was on the ship but was never a member of the senior staff until later on AFTER Khan left the Enterprise. Perhaps then Khan saw Chekov somewhere on the ship that was never shown in the television show (Trekkies, they'll think of anything to explain something away so the universe stays consistent).
5) I imagine the canyon is because of ship building or mining. Don't ask me, though. You also need to remember that at the end of the 20th and beginning of the 21st century in the Star Trek universe, WW3 took place. There was also the Eugenics Wars that took place before that. Lots of shit happened. It would be possible to assume that at some point, the detonation of a nuclear weapon (nukes were used in WW3) created a canyon.
OK for ya, pumpkin? Got your closure?
