I almost forgot to specific note on Part III - maximum defense.
Even with a skill cap and a DB cap, it's possible to push defenses so high only a critical matters.
The maximum defense you can get with Skill 25 is Parry 15, +1 for CR, +3 for Enhanced Defenses, and +6 for DB (before Retreat and conditional modifiers.) That's a 25 to hit, and a 25 to defend. Skill 30 allows for a 28.
If the maximun penalty you can inflict without special techniques is -8 (Feint, VDA), that reduces the 25 to a 17, and a 30 to a 22.
Therefore it might be useful to have, instead of a DB maximum, a defense maximum. Set to, say, 20, no points in excess of 20 count, no matter the source. Cap at 20 before penalties. So Skill 25 guy above actually has a 25, maxes at 20, which is a 18 vs. a DA, 16 vs. a VDA, 14 and 12 if Feint is added in. Retreat still matters against very skilled foes, and you are discouraged from wasting points on advantages and skill points that simply cannot usefully add to your defenses.
This kind of rule puts a bounded limit on overall defense keeps everyone potentially vulnerable, and means multiple defenses always have some cost. It also nicely allows for PCs who aren't very skilled to pile up DB to keep themselves alive by alternate means. It also gets rid of the issue of people exceeding the maximum skill through Grace spells or potions or Heroic Feats to raise defenses - it simply doesn't matter.
I'd put this limit in before Feverish Defense, if you're using Extra Effort in Combat.