Chi improves critical hits - damage and effects.

About bloodlust - keep in mind that high levels of it make your fighter more likely to miss (for Wars there is Battle Hardened to partially address that) and endurance is exhausted faster. And don't rely on it too much to boost damage - sometimes it does that quite noticeably, sometimes you won't see any effect.

Yes, Pole Arms get their damage improved mainly by Agility but Strength also contributes.