1-to-1 NAT needs a fixed WAN IP. The easiest solution would probably be to configure your unused NIC as DMZ and connect your IPTV box to it. Without reading up on the manual for whichever box you have I don't know what the box needs to receive from the WAN so I can't offer any advice on how to effectively set up the firewall. As a thought, have you tried installing the miniupnpd app? Perhaps the box will then work directly as it may be able to set up its own port-forwards.

Hi, Thanks for the response. I have a Cisco IPTV box for TV service by my fiber provider that I'm trying to get working behind my new ClearOS install. ClearOS is in Gateway mode, and it has 3 NIC's, currently 1 External and 1 Internal, with the 3rd unused. My ISP addressing is DHCP so unless there is a word or placeholder like 0.0.0.0 (which I tried), I can't seem to be able to do 1:1 NAT to a dynamically assigned interface. Would the best thing be to try throwing in the 3rd port on ClearOS as DMZ and create a DMZ VLAN tagged to the switchport the IPTV box is on? Or HotLAN, possibly..

Have to take a look at VLAN's on the procurve switch I have, very odd interface on them...

That sounds like you have completely bypassed the firewall. Or are you talking about letting anything from the LAN to the WAN? That is normally allowed by default.
What do you want IGMP and Multicast for? Is that for your internal LAN traffic or from the internet to the LAN?
How is ClearOS configured? And how many NIC's does it have?