My girlfriends psycho marine dad is after me? How would you deal with him?

You say "she's freakin' 17" like that makes her an adult. Until you're older, you won't realize just how young you still are. You just got some dad's precious baby girl pregnant, so he has good reason to be pissed. Go ahead, report him to the military, see how far that gets you. They'll be more sympathetic to him, because now you've distracted him from doing his job.