Thanks for the kind words! I'm glad your doomed group of adventurers had a fun time.
With regards to the betrayal elements: there is a mechanic built to support that style of play, though it doesn't appeal to everyone. The Reduction Roll kicks in when a player is at 5 Ruin, right on the brink of losing their character. They can then start betraying the party in order to lower their own Ruin and claw back a bit more time before they're lost.
I love the idea of adding time pressure to the game. Because your characters aren't built to last, it makes sense to discourage players from too much planning (instead of doing the dangerous and exciting thing!) Go punch that bee! Touch the gross thing! Wander off alone! Tell the best story!