I don't trust any binary, but i have to use nvidia video card driver.
Since xorg/video drivers runs as root and needs to access my hardware, is it possible to block internet connection to these drivers?
Sadly, no. A process running as root can simply override any limitations put on it.
Actually, running the xserver in a chrooted environment with some hacked up net libraries might work, but that's way beyond the scope of what I can type out on my phone right now.