Brentil, Can you ping the IP address of the router? Maybe you can try to change the wireless channel to see how it goes.:)

As far as I am concerned, TL-WPA281 will have its own network even it is called a extender. Since it has a different network, devices cannot roam between two different networks usually. Maybe you can...

Have you tried to reset the modem and reconfigure it? How about the wireless channel on the modem? Maybe you can give a try to change the channel to see how is the wireless going.

Do you mean the PIN number for QSS? that's the one you can find within the router's web interface. you will find an option for QSS or WPS, and the pin number is showing there.

I think you can go to check whether you have selected the correct country and mobile ISP or not? check the the solutions here: http://www.tp-link.com/en/article/?faqid=269 It may give you some...

I know there is a FAQ for port forwarding, here it is: http://www.tp-link.com/en/article/?faqid=134 but it seems that's pretty old...hope it could give you some help.:)