I concur with most of this. We will definitely not be completely correct, Jim loves to see us squirm, but we are headed in the right direction. Harry has been forced to deal with increasingly dark stuff, and for the entire series it has been about him knowing where the line is. So yeah, Mab testing Harry tracks, also conflict with the WC makes a good deal of sense, as we have seen how screwed up it is with every interaction we get.
I agree that Mab is not Evil, imo just a really weary/tired battle hardened General who has been fighting for mortal kind for millennia, and won't take crap from some know nothing uppity mortal much less a herd of cowardly wizards. She has referred to herself and Harry as wolves more than once, so she completely sees how the WC has degenerated and despises them for it.
Edit:
That being said, I can't see Harry being the defacto Merlin of the WC 2.0. He would be mostly symbolic figure head than anything else.
Also, I have serious concerns on whether or not he will actually survive. Being a fulcrum for existence doesn't tend to work out for the fulcrum. We know that these stories are his journals which does seem to indicate he will live, but there are so many ways that could actually come about. I.e. he dies in the trilogy but due to his foray in GS he becomes something similar to Bob, etc...