Compulsion vs. Changebility in "The Changeling," and The Fake Physician in "'Tis Pity"

In Epicene, we encountered the role of "the humor," a character whose irrational attachment to a state of mind or way of being in the world becomes a blocking mechanism for young love and a butt of many jokes and hijinks. In The Changeling, to what extent may we read De Flores' compulsion to chase after Beatrice, despite her cruel treatment of him, as a darker reworking of that comedic convention? And how should we situate or make sense of this sort of compulsion in a play which, as Engle points out in the introduction, is so populated with characters who suffer from their own and others' inconstancy?

In thinking about 'Tis Pity, I find myself feeling curious about Richardetto's (somewhat improbable) ability to impersonate successfully a well-respected physician. From a practical standpoint, his disguise is certainly an ideal one in providing him access to private homes, while his assumed role as "keeper of the body" seems metaphorically appropriate when we consider how he intends to preside over the death of Soranzo and the coupling of his niece and Bergetto. Yet what does his ability to feign doctorly expertise so convincingly tell us about knowledge and authority in the world of the play? And how does his somewhat perverted use of knowledge reflect or complicate how we perceive Giovanni's self-interested sophistry?