1. Port check websites are wrong 9 times out of 10. They only work under strict set of conditions..
The only way to test is to see if it works.. if not you need to give us exact details of what you did and what ports you opened.
2. Check the IP is not via double NAT.. it will never work without public IP on the TC WAN port.
See Re: Help Portfoward
Same problem.. port forwarding for Minecraft won't work and never will because of double NAT.
3. Microsoft build their games for upnp.. some routers are on the list .. no apple router will ever be on the list because Apple uses NAT-PMP and the two are like VHS and Betamax.. apple therefore don't care if your games and consoles and PC and everything else in the world work or not.. they cannot manage to include upnp in the firmware.. whereas other manufacturers of routers do have both...
4. I highly recommend using the TC in bridge therefore and a standard.. compliant UPNP router in front of it.