Your xorg.conf is a big giant mess. You can achieve what you want with an xorg.conf containing five, maybe six lines. Not kidding with that. I'd have to look at the documentation to figure out the correct Metamodes syntax though. I know how to do it from the commandline, but it requires a patched xrandr utility. With that patch, you do something like:
xrandr --output LVDS1 --mode 848x400 --scale-from 1920x1200
I don't have time right now, but later today I'll provide that patch and also go through the nvidia documentation for the Metamodes.
Edit: Here's the xrandr patch that activates the scale-from option: http://article.gmane.org/gmane.comp....l/30138/match=
About Metamodes, I'm having a lazy moment
, but basically, you need to set ViewPortIn and ViewPortOut. The Nvidia documentation has all the details.