Looks like, because you've got the "UseEDID" "False", the driver is sticking to a default size of 640x480. Hardly surprising, really, as it has nowhere but the EDID to get the resolution capabilities from....
If you remove;
Option "UseEDID" "False"
Option "UseEdidFreqs" "False"
and just leave in the;
Option "ModeValidation" "NoDFPNativeResolutionCheck"
then you _should_ be able to get the 1280x1024.
There definitely seems to be something odd about these EDID problems with flat panels. Maybe the manufacturers are not quite following the spec, whereas that's what Nvidia rely on - who knows :/