The port can be wan only when it is working under ewan mode but under ewan mode. VDSL will not work. So I don't think the backup solution will work

I think you can move the repeater closer to the router to test, or check for update of both repeater and router

I think you can do that. Or use tether app to cofig the extender

did you check the wan IP address and gateway on your router and make sure they are public IP not private

yes I am sure, on the spec it says Selectable 300Mbps at 2.4GHz or 867Mbps at 5GHz dual band Wi-Fi, and I also checked their Emilator too: http://www.tp-link.com/en/download/M7650_V1.html#Emulators...

did you try some public drivers? it looks like a compatibility issue