What country requires you to have a green card to be able to renew your passport???

Like the person above said, immigration pretty much looks at your relationship after you guys get married, not the past 5 years unfortunately. I say get married now if that's what you guys want, why wait. And in the mean time, start to get things together. Keep track of skype logs, texts, mail, plane tickets (if you guys travel to visit each other), etc. If it's obvious that the marriage is real, it shouldn't be hard to prove it. You both can explain the distance through detailed affidavits and submit them with your application.

Definitely recommend seeing an attorney too.