This server requires about 2048M to run. A 3.2 GHz core will support approximately 24 players. Since Pavlov VR is single threaded, faster clockspeeds will mean higher performance.
If you are running multiple servers and have set additional ports (see http://wiki.pavlov-vr.com/index.php?title=Dedicated_server#Running_multiple_servers_on_one_host) then you need to allow access to the defined port plus the port 400 higher. So if you use 7000 as your port, then UDP 7000 and 7400 need to be open.