Maybe a pet peeve of mine, but I've never been a fan of Vault-Key. Every time you draw one of the components of the combo, make a note as to whether you'd rather have something else. I've played against Vault Key many times and only lost to the combo once IIRC; can't remember how many times I've smiled inwardly when my opponent dropped Key or Vault, but didn't have the other piece, and gave me virtual card advantage. Synergy is great, but these cards do almost nothing of value on their own.
I'm also not huge on Top, as it requires you to constantly sink mana into it and generates no card advantage by itself.
These thoughts are probably at least somewhat heretical; as always, think through what makes sense for you and test things out.
Edit : Just scanned through your list again. Hurkyl's seems a bit suboptimal; you'll buy yourself one turn vs. Workshop, and then what? You aren't a combo deck, so your opportunities at that point seem underwhelming. Maybe a By Force or Shattering Spree (tho probably not enough red for that one).
So whats the reason for the one crop rotation? Just one seems weird.
Yeah, since you're not running Null Rod main, Expedition Map seems like the better choice.
I love 5c Stax and would love to see it come back, but running so many Karn, TGC seems iffy with that mana base. Running a few Maps to search for Academy would definitely help.
Combines Force of Will and Negate.
Card works as advertised.
Yeah, I just see this as too narrow to be played maindeck in Vintage. Maybe as a one-of. You can only have a certain critical mass of pitch counters before you just lose the card advantage equation; especially if we're talking from a mostly defensive position.
Could have a home in the sideboard... I guess it also helps push through your Ancestral in opponent's upkeep.