Answer:
1 Ralph believes that Jack would always try to hunt and kill him because Jack has become more savage and barbaric over time. Jack is no longer interested in being rescued and wants to be the leader of the tribe, which Ralph stands in the way of.
2 Jack and his tribe are planning to hunt down and kill Ralph. They believe that Ralph is weak and not fit to lead the group and they want to take over as the new leaders.
3 The twins are helping Ralph because they still see him as the rightful leader and they are afraid of Jack and his tribe. They also feel a sense of loyalty towards Ralph, who has always treated them kindly and protected them.