Minor thing, but regarding Balance: I think it should say "When you deal damage during battle you may choose to do -1d4 damage." Or otherwise indicate that it must be vs a foe.
Without that clause, a druid could arguably use this move while punching his willing allies. If they choose to not defend themselves, the druid just does damage (no move required). If he's unarmed, he "might do 1 stun damage." If he then chooses to do -1d4 damage, that's 0 stun damage. He then heals someone for 1d4 damage. And is the ally even stunned, since he took no damage?
Yes, this is easily prevented under the "don't be a tool" clause of your social contract. And sure, you can say "you're unarmed, so you can't deal damage." But that implies that I can't ever do damage unarmed (if I can't do it NOW, when no one's stopping me, when can I?). Frankly, I don't want to have that conversation at the table. Also, it's an easy enough fix to make.
Possibly a broader concern with the move: it's very mechanical. There's no required fictional component, just the implied fictional component of dealing less damage. Maybe make it something like:
"When you deal damage in the heat of battle and choose to pull your blow, do -1d4 damage and gain 1 balance..." Something like that; maybe come up with a more poetic or evocative phrasing than "choose to pull your blow."