Re: black screen when I startx
It looks like a CRT is detected but it might not be the right one. Is there an external monitor attached? What's the HorizSync and VertRefresh set to in the Monitor section? Try removing those and let it use EDID. You problem sounds related to the HorizSync en VertRefresh frequencies.
You may also need to play a little with the ConnectedMonitor and/or UseDisplayDevice setting.
Yan can also try to setup the xorg nv driver first so you know the setup works, then move on to the nvidia driver.
Post your xorg.conf here too so we can take a look at it.