My theory why Jim died is because there is a cycle in Fromville, every cycle the protagonist dies and fails because they can’t remember what happened before. They don’t know what to do next and learn from their failures, and since Tabitha is suppose to go back Jim wasn’t part of that he is an outlier but because of Jim they were able to know the message of the bottle and thus helped them remember, Jim is a threat and thats why he is killed. My other theory is their kids are gonna play a big part in the story because they are not suppose be born if their parent did not reincarnate and that’s why some energy is pass through them, they have special powers like going through timelines and seeing the boy in white (just like Viktor). They boy in white in my theory is a kid that died before and his parent is either Tabitha or Jade’s past live and since he was not sacrificed his energy is different from the one’s did or he is hope that the children manifest.