The answer to the first question--if Lady Catherine truly had condescension--would be yes: during Jane Austen's own time, the majority of applications of condescension are strongly positive.
Burrows studies small words like quite and very, but condescension, too, was undergoing shifts in Austen's era.
Specifically, novelists in particular, and at least one moralist, were becoming suspicious of condescension in the early nineteenth century, when most writers still used the word as honest praise or even as a divine attribute.
Condescension soon expands its applications, and yet a sampling of the first forty Google Books hits on the word from the years 1712-1718 still shows twenty-six distinctly religious uses.
One thus finds contemplations upon or discussions of the term, as in dictionaries, here from 1813: "Deference is an ascensive, condescension a descensive, and complaisance a level attentiveness.
When Jane Austen puts condescension repeatedly in the mouth of a clergyman, the choice is therefore utterly appropriate to his profession.