How could killing themselves possibly help people get out of the loops?

It's important to note that there are various areas with their own loops and their own loop duration--from a few seconds (the tent loop) to several years (the camp's loop). That's why some of those stuck in the loop are being driven crazy by it (like Carl) and some seem alright with it (like the camp residents).

As for why some characters commited suicide:

• Carl, apparently, has been playing with suicide for quite a while, saying, "you get used to it--suicide option." He realizes that he's probably stuck forever ("if you let it have you and you're still in the borders when the loop resets, you'll be stuck as shit forever"), but keeps committing suicide because he doesn't know how else to try to break it, I guess. It seems to be a form of escapism for him (he complains "it doesn't let me dream, it does it so my mind never leaves this place, these three hours") as well as a form of rebellion (he shoots at "the thing" and screams at it happily before he shoots himself).

• Michael sets his house on fire because, in Michael's words, "the one thing I do know for certain is I would rather reset things on my terms than let that fucker do it for me..." He also mentions "I keep thinking there's going to be this configuration that's going to break us out of the story...", so it seems like he hasn't given up and he keeps experimenting.

Apparently it's pretty excruciating going through the time loop reset. Carl mentions this when Justin first meets him at his caravan. Carl seems to think it's better killing himself than be alive when time resets.