As far as i figured it out, steadiness just means your aim quality. It’s gets reduced by firing (recoil), for example, and increased by spending turns (press [.]). Confidence is some sort of how much of a chance to score a hit your character thinks there is. Increases by skills, better guns, some mods (maybe), and reducing range to target. Decreased by encumbrance, increasing range, etc. More of both means better CTH, more damage, bigger headshot chance.
