Quadro FX Go 1440 lower resolutions (1920x1200 native, 1440x900 preferred)

[Valtam]

And considering using the real nvidia driver is preferred, why wouldn't I want to use it?

Preferred doesn't always translate to best in linux. Sometimes, the open source drivers outperform the proprietary ones, which is why I would still like to know why you need the proprietary driver. This is a graphics chip from 2005, what modern games, rendering etc do you intend to run on a 11 year old gpu?

Plus this resolution was available on Windows with NVIDIA so I'm a little puzzled why I can't get this to work still.

Because you cannot compare the way Windows and Linux drivers are written and maintained.