If you wish, and if you understand the security concerns as raised by Derek Zeanah then you can have the configuration you want. All you have to do is to add rules into the PFSense firewall configuration to allow the ports you need through the server. Just make sure you add them in both directions.
As Derek Zeanah said however, you should really have a firewall or other security appliance on the outer edge of your network, even if the server is supposed to be internet accessible.