First, did you try rebooting your router? That's what got it working when I tried to test this.
Have you tried to get remote access to work with the standard 9090 port? (externalIPaddress:9090/gui/)
That would establish that regular port forwarding works. Then you can get more complex with mapping of 9099 to 9099 in your router. The BitTorrent port for transfers is not important for this remote access problem (though it is relevant for download performance).