Grevane is one of the (non-Cowl) necromancers that Harry faces in Dead Beat.   IIRC , Ramirez shoots him.

So it seems to me McCoy laid down the cloak and picked up the staff as part of the same general event.

Well Krakatoa was really big and is around the time Jim said Ebenezer first picked up the Blackstaff.   It's not impossible that the previous Blackstaff died during the event and that Ebenezer's first act upon picking up the Blackstaff (in desperation?) was causing the boom in a last ditch effort to stop whatever it was.

Sorry, I was really focusing on the Questionable part.

Remember that Mab calls Rashid "that desert Fox" back in Summer Knight?   Mab uses the same animal earlier in the book when she tells Harry about the myth of the Fox and the Scorpion (with herself as the Scorpion). 

Coincidence or reminiscence over previous encounters with the Gatekeeper?

Also, fwiw, I have a strong suspicion that Mab's "Executioner" mode is directly related to Angels; since she almost perfectly resembles the Angel of Death we saw in GS, it makes me think that once upon a time, an Angel of Death might have met its end on the Stone Table.

That might just be because of human (or Harry) perception. 

I don't think I like the idea of sacrificing an Angel on the Stone Table; it doesn't quite fit.   As Bob says "different wavelengths".   And from a technical point of view, how would you give equal power to both sides?   Remember that the Queen in charge of the Table at the time gets the power.

I imagine that the Outsiders are the real Adversary that beings like Uriel have to face off against,

Thing is, I don't think we've ever see any angelic forces fighting directly against the Outsiders.  I mean (as far as I remember), you've got Michael at the end of PG, Nicodemus' "blinking" when he hears about Hellfire at AT (and some of the stuff he says in SG) and (if you buy into the theory) Rafael-Demonreach.

Now granted the whole Outsider threat was only explicitly stated in the last few books so its not impossible that we haven't seen the whole picture, but given that a whole angel is given the sole job to protect the possibly dying Forthill, you'd think Harry would have run across a few hints of their existence at the continual war at the Gates.

I guess it I just haven't have gotten "that vibe" so far, though of course it might be Harry's misunderstanding of the situation.

Good point.   The sculpture vs picture metaphor Harry uses very much suggests your reading (both for the Walkers and Mab).

I guess I always felt the Mab's defense of the Gates was against similarly-weighted opponents.  At the very least, this vastly increases the amount of "computing power" the Outsiders potentially have, even if they are constrained by amount of power they can project onto our "flat" 3d world.

I have no real problem with the idea of Creation bubbling out of Chaos, more that on an aesthetic level I dislike the idea of that bubbling chaos being both a)the literal and direct animating source of all Life while also b)being a conscious malevolent entity of destruction and madness and despair and all the other things that Ive culturally been taught to associate with all lovecraftian deities. 

Azathoth isn't really malevolent.   He's the "mindless god".  It's just the he's so alien that any contact with him leads to madness.   Another example would how certain bacteria can grow and prosper in your body.   When you kill them (by taking antibiotics) it has nothing to do with malevolence. 

When I say "local" I meant local to that individual universe (including it's accociated NN), meaning there might be mirror versions in other universes.  This becomes an important distinction because I do not think that is true for Outsiders.   There is that line from CD about how the outsider seemed not bigger, but rather /deeper/ than things like Mab, a photograph vs a sculpture, and the WOJ that Outsiders are just Outsiders and only look different depending on what universe they are trying to get in.  If each universe is a single "disk" cross-section of giant a World Tree branching out in Time, then the idea is that the Outsiders are all the negative space between and around that branching tree of Creation.  And by extension that, unlike universe-level creatures, there is only one HWWB4 out there, and right now he's looking at Harry's Universe.

I have no problem with the idea that the whole multiverse is merely a single bubble in the Outside. 

Not quite sure what you're saying about HHWB.  The way I see it, either he's a minion -- one who can only manifest in one universe, or he's more along the lines of Uriel -- sees multiple universes at once.  I don't think this has been decided one way or the other.