I'm not aware of any cases in the Bible where someone was healed or saved who wasn't interested in being healed. I suppose you might count children who were healed at their parents' requests, but I think it's safe to say that God hasn't given us a record where He's overridden someones free will.
So how would you go about praying for the restoration of a marriage when one of them either isn't a Christian or is at least a "fire insurance" christian? I mean you can pray that they would be open to salvation or open to a real commitment to Jesus, but when they've shown year after year that they're not interested in being anything other than they already are... I guess that's praying for a miracle. I still know better than to think God will force a person to believe. So at some point the two are bound to wind up at odds with no solution.