Do you want all your internet traffic to route through the VPN? If so take a look at this link:
click "Connect or disconnnect...",
right-click the VPN connection,
click the "Networking" tab
double-click "Internet Protocol Version 4 (TCP/IPv4)",
click the "Advanced..." button,
and there it is: "Use default gateway on remote network".
Re: How many VPN users can your VPS handle. This will depend on what the VPN users are doing, what the VPS is already going and what bandwidth is available to user and the VPS. How many users were you thinking?