You probably already have a better handle on it than I do, but as for your last question: Yes. "When each of several adjectives preceding a noun modifies the noun individually, the adjectives should be separated with commas: It was a large, well-placed, beautiful house . However, if the last adjective identifies the noun rather than merely modifying it, no comma should precede it: His is the large brick house on the corner.
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Mister MicawberHowever, if the last adjective identifies the noun rather than merely modifying it, no comma should precede it: His is the large brick house on the corner."