Unfortunately the only decent ruler I have is 600mm in length -- I'll double-check the numbers with my measuring tape, but that's bound to be off a mil or two in either direction.
Based on the photos and my recollection of the camera angle (which was a bit crappy, sorry!) it's 324+328=652mm for the E/A, like you say, but 324+323=647mm for the top four strings. That seems surprisingly far back for the factory to have put the holes, but there we go.
Am I understanding you correctly, that for the higher strings, sometimes you wind up having a smaller distance between the bridge and the twelfth fret than you do between the fret and the nut?
Nice idea about getting a longer screw! Presumably they're standard M-something ones that the local hardware shop will sell.
Sorta-kinda tempted to just wait for the tuners, put them on, then screw on the bridge, and then string it up and see what it needs, then move the bridge if necessary. The problem with that, though is that right now the screw holes that are there could probably be filled with glued-in dowels and then new screw holes drilled. But once a screw has gone into those holes, I'd be worried that doweling them won't give them enough strength to handle a new hole right next to them.