A230 I would say yes, looking at the rules, I can see nothing wrong with it.

A231 Stunning Fist is part of an attack and triggers when the opponent is damaged by that attack, so yes, I would assume that you get to make an unarmed attack although it's unclear whether you actually have to roll to hit the pinned creature or if the damage is part of the pin (I'm leaning toward the latter option).

A232 Since you can only use this ability when expending points from the ki pool, you most likely only gain its benefits when doing so.