The standy mode on the PLC devices can be turn off through the tpPLC utility. You can find the utility on TP-LINK websites.

Cable is not plugged in in the WAN port on the router. The WAN LED is not on, right? If it's plugged in, it could be the cable is bad, or the WAN port of the router is broken. Change the cable....

Which default filtering rule you chose? Allow or Deny? I don't see any Rule added.

I suggest you update the firmware of your router.

Your house is big, 170 square meters, it's hard to get all part covered with one router even it's a high power router. I would suggest a range extender or powerline extender, or newly Deco M5

Did you send email to support.it@tp-link.com? Or called Tel: +39 (02) 92392214 Service Time: 9:00 AM to1:00PM & 2:00PM to 6:00PM, Monday to Friday.