You have your Beryl in the DMZ of your main router? Are you sure you want that? All the traffic will be forwarded to the Beryl. That's not very safe unless you know what you're doing.
I suggest that you try to forward on the main router rather than dropping the Beryl in the DMZ. It might work and it’s safer.
Your main router connects to the WAN port of the Beryl, correct?
For port mapping on the Beryl, try:
TCP/UDP
Map the port that you want to forward. External is WAN, internal is LAN. Use the same port number for both.
Internal IP should be the server's IP (torrent client).
Try that and make sure the client is running and listening before you test.
You can use something like: