Armor Maneuver Penalty does not affect DB at all. Also, wearing armor is not a maneuver, so as you don't roll against armor, ArmorMP doesn't affect your final reduction. I actually don't think there's a case where you'd make an Armor roll, so the penalty doesn't apply to the Armor skill.
I admit there is some confusion in what is and isn't a Maneuver, but in the "isn't" category, they may have other things that affect them, i.e., Initiative and positioning plus what combination of weapon and shield you're using. A full suit of "studded" leather is DB 30, period.
And the MP only applies to skills that use Ag or Qu (inclusive or in this case).
However; the MP does affect the (2*Qu) to DB, that said it cannot reduce it below 0 regardless of how much the MP is.
