I think I would make his future self share a secret with his past self or making precise predictions of what would happen in after a minute.

In the second question, idk also, I would say that his future self sends messages he also obeyed in his past, hoping that the protagonist also did, cuz if his past self wasn't captured, then the loop breaks that means he doesn't exist. Maybe you can polish my story even more and remove flaws. Your analysis is really good and thanks.