Question: When Tuck is inside Jack he can't go through the heart - is this because Jack would have a heart attack or because Tuck would die?
Answer: I would say both probably.
Question: Why did Lydia leave Tuck?
Answer: He was a drunken, careless and inconsiderate guy, who never took responsibility for anything. If that's the way he treated his girlfriend, how would he treat the baby.
Thank you I always wondered that.
Answer: Probably, but most likely it's because Jack's pod is fragile and wouldn't survive the shock wave heartbeats. The pod is experimental and built for scientific observation, not battle.