I thought the show got better and better as time went on, from sardonic comedy to real adventure/drama. The final episode is a textbook example of how to write an adventure script.
1. I think that was being left for the second season, if there is one.
2. There’s a strong religious subtext and we knew early on the Frankie might be the messiah. Definitely Jamie was a Christ figure (with a touch of Moses) and I think the idea of Ariel as Satan is clearly hinted (he even had the name of an angel, though not a fallen one). Jamie, too, comes from James, an important name among Jesus’s disciples.
3. One small nit: it really didn’t matter if they got to the bunker before the asteroid hit. If it landed on the bunker, they’re dead anyway. If it landed halfway across the world, it would take time to affect them; probably months before plant life died off. It added urgency, but there was plenty of time; the main point of the bunker is really to save people from hungry mobs, not the comet. That’s what I expect will save Jamie in season 2, if there is one.
4. Project Savior was a genuine attempt to deflect the comet, but it failed. The bunker was the fallback.
I hope there’s a second season; the main issue would be to get some of the bigger names back (Mullaley and Fischer). Sky1 could probably continue if they can manage that.