My solution.
Firebox OS 11.2.3
Via WatchGuard System Manager create two custom policies, one for inbound ports and one for outboud ports like so.
Inbound
From: Any-Trusted, Any-External
To: (Static Nat) {External_Interface} --> Server
Ports: 80 TCP, 554 UDP, 5005 UDP, 1755 TCP, 1755 UDP, 554 TCP, 3000-3250 TCP, 3000-3250 UDP, 3889 TCP, 135 TCP, 135 UDP, 1750 TCP, 3889 UDP.
Outbound
From: Server
To: Any-External
Ports: 80 TCP, 554 TCP, 5004 UDP, 5005 UDP, 1755 TCP, 1755 UDP, 1024-5000 UDP, 3000-3250 TCP, 3000-3250 UDP, 3889 TCP, 135 TCP, 135 UDP, 1750 TCP, 3889 UDP.
This rule allows all HTTP, RDP and MMS-RTSP Traffic to flow to and from a server behind a WatchGuard, my specific issue now resides with the modem on the external interface and is being rectifed by other means.