No pushing of gateways is required, that gets handled automatically when the client connects to the OpenVPN server.
You can watch the process in action.
Go to the OpenVPN client icon, rgt-click->Edit Config then add the line "Verb 5" to the end of the config file and save it.
Reconnect the client to the OpenVPN server and "View Log" on the client after it connects.
You'll have a whole bunch of excess verbage, but near the end you'll see some lines like:
"C:\Windows\system32\route.exe ADD 192.168.x.x MASK 255.255.255.0 10.x.x.x"
These lines execute the Windows ROUTE command to tell your client how to send traffic to the OpenVPN server's network.
What subnets are you now using for:
pfSense LAN?
OpenVPN tunnel?
Remote PC's LAN?
These three items must all be unique networks as we said earlier.