As you said, you have passed through the Dual 10Gb NIC to a VM. VM doesn't "know" anything else than its own existence thus able to serve the host (UnRaid server, as it's not physically connected to it). You need to add virtual NIC to the VM and via that the host can communicate with the pfSense VM.
See the following thread for more info:
FYI: If you're running UnRaid on trial basis and you reboot your server, the arrays and firewall VM won't be started automatically. This is due the limitation where the UnRaid will start to fetch your trial license status from the Internet, and because the routing is based via VM, it wont be able to do so.