Re: Fullscreen problem.
Refresh rates can be specified individually for each resolution in xorg.conf, but make them all the same. I forget how this is done now, because I always keep the same resolution and have no need to go lower... eg it was "1024x768_85" for me.
The lower modes may not be enabled, even if you specify them. My laptop only likes 1680x1050 for example. See if you can get a lower mode like 1280x1024 manually by pressing ctrl-alt-plus (plus on num keypad). The X log will report whether or not specific resolutions are possible.