Herewego makes an interesting observation which i didn't realize before. My confusion is somehere else!
Let's say scenario one is that:
JGL kills willis from the future...closes the loop and goes on to live the next thirty years... then in that particular time-line why should there be a rain maker character? because it is scenario two where Willis survives and goes on to kill the kid's mom that eventually turns the kid into the monster called rain maker. So in scenario 1 there shouldn't be a character called Rain Maker.
Secondly as JGL develops relations with Sarah and the kid it should also affect Bruce Willis's memories, thought process and alter the future that he came from.
Everyone can be a force for good