The Dead Zone: Denouement

Johnny: "All this time, we thought he was a puppet. We thought wrong, Gene."See, I knew Greg was still evil.How would marrying Sarah have stopped Greg from causing the Apocalypse? Does Greg truly have feelings for her? Would he have tried to be a better man for her sake? Or would she have discovered his true nature and found a way to stop him? (I'm guessing that last one.) After Johnny