Sorry, I got interrupted just now.
Your new OPT1 interface is just like any other interface but you do have to create rules to allow VMs access out from the DMZ - to send emails for example.
You say you have port 80 forwarded to your mail server? I assume you have port 25 as well or just made a mistake there.
If you only have one external IP address then you would only be able to forward any given port to one destination IP (VM or physical machine on your LAN).
I can't answer the PS3 problem but, by default, anything on your LAN should have unrestricted access to the WAN.
Hope that helps.
Just re-read your post and realized you might be asking about creating a physical DMZ - which I assume would be connected to your PS3. Not too much difference between that and creating a virtual one - you just need to join a physical NIC to that vSwitch. It would still be OPT1 to your pfSense VM.