Actually, you can do each of the suit requirements at the same time in the same level, regardless of what level you're in. For instance, try pulling (NOT just hitting) something with the chain 30 times, or killing (I think it's 20) a number of enemies with the dash-slash. Nothing to do with your end rank.
The ranks also aren't a factor of points, at least not heavily -- in the jungle mission, for instance, you're told to rescue five reploids. If you don't rescue those five, the mission wasn't successful, even if it was completed, and thus you can't get an S rank.
it's the EX Techs you need an S rank to get. S rank any given boss to get one.
-Tempest out.-