Where to start...
Your "non-GPL license" message is not an error, it's just a warning. insmod did not fail, and the driver installed just fine.
You can't uninstall the RPM because you were probably using the .rpm file name as an argument to rpm -e, right? That's not right, the rpm database entry does not contain version numbers or file extensions. Do an rpm -qa | grep -i nvidia to see the rpm database's package name, and run rpm -e on that in order to uninstall it.
/dev/nvidia didn't exist because you are using devfs, and only the device files that exist as hardware are going to be in /dev. You're fine.
If you want full dualhead support, trash Xinerama, and enable TwinView instead. That way, you don't need multiple Device or Monitor sections at all. Read through the README for how to set it up.
You can't set the primary display regardless of how you set up dual-head support, though, I don't think.