have you guys tried to disable the "WMM" feature?

Do you have any server/service working on port 8080 9090 on your computer? If there are not, and you use some test website to test it, the result will be ports are closed, but they are actually open....

Do you have a 300Mbps NIC? You can check the connection speed to check if you get the full 300Mbps. There are no setting on the utility to keep it from switching back to 20MHz on the web utility page.

The limitation of DHCP reservation is 8. I'm afraid there are no way to improve this , unless TP-LINK update the firmware

You know some ports are occupied by the router, like port 80/21 if you enabled remote access feature of the router. You can try to set your NAS as a DMZ host, or use other ports.

Is it 10MB/s, or 10Mb/s? The peak 5G wireless speed of WDR3600 is 450Mb/s, but its actual speed can achieve is approximately 200Mb/s, that is 25MB/s. If the NIC of your WD MyBook LIve is 150Mb/s...