Is there anything connected to your ‘line’ before the master socket , is it possible you have an extension ( even if there is nothing connected in it ) wired from somewhere other than the removable panel of the NTE5 like an external block on the house wall with one cable to the master socket and one to , for example, an upstairs socket ?, if there is something like that then using the test port doesn’t achieve anything .
Assuming you don’t have anything like that , so either only the master socket , or if you have extensions they are correctly wired to the master socket consumer panel , remove the panel ,plug your router into the test port and post the router stats while connected in the test port.
Although you said you have done this , and observed no change , you didn’t post the results, if there is no change ( which is quite likely if there is nothing wrong with your internal setup ) then either your line is fine and the current speed is as good as it can be , or there is an issue externally affecting your line’s performance
