We need to knock him out -- only way to do that is to make his non-lethal damage exceed his current hitpoints.
A good strategy might be to hit him once or twice (and not hope for crits) and then switch to non-lethal, or just go with non-lethal all the way.
Marot would be pretty poor at dealing non-lethal damage -- he couldn't use his eldritch blast for that, and he is a lousy melee combatant (with a -4 non-lethal penalty to hit)
I may hit him once with an eldritch blast, but Marot would feel incredibly guilty and remorseful, possibly unable to bring himself to it, unless he rationalized it some way in his mind.
And, I think this needs the obligatory "You be evil Stonegod" from your sig.