Where is Nix?
He's not there.
This tells me he's either hidden from view in front of the 'north peristyle' (see Roberdeau's map) or he's somewhere on the south side of Main Street, possibly near the 'south peristyle'.
In the Nix film there's a moment, just after Hill has managed to get a proper foothold, that the limo passes behind a lamp-post.
This tells me he's not in front of the north peristyle as there's no lamp-posts there for the limo to pass behind. Therefore he must be somewhere on the south side of Main Street.