How do I know if I'm making the right decision?

No, all of that sounded like one bad decision after another. You're 17. Why would you wait around for some 24 yr old ex military broke guy who's having a baby with your cousin? Is that really who you see yourself with? To me, it should have ended before it began, not only because of what a struggle his life is, but because he has a kid a cousin. That's family. Don't buy all the BS he's talling you.