Can't say much now, haven't been playing it since it's an optional missionI agree that he was unable to use all his power, but I don't think he was stronger than MC, after all it's quite easy to beat him, even without using techniques. There's also the point that at a certain moment in the fight the devil took control of him, and even then the difficulty didn't increase much.
As for the lightning part, I believe it's more about the technique having a connection with the heavens than Mo Long's own power, after all if you insist on attacking it's certain death, even with resurrection.