Thanks for the thorough feedback.
You are right that this version will not get further fixes.
What you're observing, characters dying after events (unless they died in the event), is not because they were in the event, but because a timespan of however many years has passed in which they would have died anyway.
We can't let characters die of old age during events without breaking the game. So obviously, they have to die after that. There was a version where this was not done, with the consequence that if you kept your characters occupied enough (and random death outcomes didn't get them), they could essentially live forever.
So there is no doom loop; it's not spontaneous death. Use the character, don't use them, they will be dead by year x either way. How long they actually survive is based on their health stat. And the AI Krankhaus characters are kept close to their original genes, meaning many of them have high health (and those who don't, you won't notice, because they're dead). If you play them yourself, it's easy to lose the health genes, since you pair them off with other houses that don't have them. If you don't specifically select for high health (or get unlucky), the lifespan will diminish within a few generations.