Merlin... wish I COULD simply wave a magic wand and resolve your friend's dilema. But the truth is, I CANNOT ... for the simple reason that I've never been in his position. Others here have offered well-meaning advice but, ultimately, only the couple themselves - based on their mutual understanding - can decide WHERE their future lies. And, moreover, WHAT is likely to serve the best interests of both in the long-term.
Welcome, mate.