I think the key to Kim is the desire for respect. It wasn't that Howard put her in doc review; it's that when she did the thing all law firms want their *partners* to do and landed a big client, she was ignored. "You don't save me. I save me." is what made the character for me - but Howard paid no attention. Then, after all the work for Mesa Verde, Kevin ignored her advice. Acker didn't respect her either - and that goaded her into trying to save his home - but he didn't *know* her. And then after everything else that's gone on, Howard patronizes her. I think she cared about becoming a good lawyer and carving out a place for herself in the corporate world because she thought the reward would be respect - and it wasn't. So, like Jimmy in season 4 (when he gave that lecture to the poor student who didn't get the grant), she's concluded that she will never win at their game. And if she can't, then screw them, let's take some of their resources and go help other people who get no respect and deserve better.
BREAKING BAD always seemed to me a classic Greek tragedy: the hero is brought down by his own flaws - and brings disaster to everyone around him. BCS is following a similar trajectory.