...a couple of minor nitpicks, if I may:

>"Mr. Darcy is all politeness," said Elizabeth, smiling.

She means here that he is merely being polite, and does not really want to dance.

I imagine she believes he's being polite to Sir William, not to herself -- she's still cherishing the memory of the insult at the Assembly.

While I agree with most (not all) of your assessments, I think the key here is that Darcy would have thought they all were "willful misunderstandings", whether they were or not.