Ok, your decision, after a few days give me information about your network stability. See you later!

I can't see Local Network or PPPoE addresses? Modem does not normally connect direct to PC. How would you like it connected for the test? You have to create broadband pppoe connection and there enter...

Cross-over between SSID is default behavior of each wireless device It is no true

Secondly: Give me screenshot from ipconfig /all when you have PPPoE connection without tp-link. Only modem <-> computer....

Firstly: Can you give me screenshot from TP-link (Status tab) when you have internet access by WR841N?

Static IP doesn't have to be public address. Can you give me screenshot from Status tab?