I'm quite sure that PixmapCacheSize and AllowSHMPixmaps are supposed to go in the Device section and not in Screen.
I'm not quite sure how these got there, but I removed these lines and nvidia-settings still crashes. But once again, that is not the problem I'm trying to get fixed here. Being able to save to the xorg.conf file only has some use for me when using 173, but I prefer 177 even though I can't use HDMI so I won't be using the "Save to X Configuration File" button anyway.
Getting help on how to enable the HDMI output is what I'm really trying to do. But your help is appreciated anyway, thanks.