Those are all great questions I struggled with, owing to the one page restriction. In a little game full of experiments, the dueling subsystem is probably the least successful one. The only goal I really set out to accomplish was to create flavorful momentary clashes in between drawn out standoffs, the points where you decide whether you even want to fight, or talk, or trigger a virtue in some other way. Ultimately, it's all up to the GM, and if I had room to explain it, I'd write something like this:
'Discuss with the players the details of the confrontation, where they stand, and what they're preparing to do. NPCs wear their intentions on their sleeves and always take advantage of their strengths. Positioning and momentum are determined by the lead up to the fight, who is best suited to the environment, and who is taking the initiative and being proactive. If the player isn't clearly better in these circumstances, give it to the NPC.'
The duel actions never result in obvious outcomes when paired off, which may reflect a certain messiness to fights, but may not make for the best gameplay. I suggest letting both fire off as 'strongly' as possible. Duel rolls should usually result in a hesitating standoff, or both parties getting badly wounded, or one party getting thrown on the ground while impaling the other party. I would love to have a compelling back and forth mechanic for swordplay, but this just wasn't the game for it. All you have to do is let things be dramatic!
Thanks for the kind comments, I really appreciate it.