PA7010P has gigabit ethernet port. If you have around 200Mbps bandwidth, it's suffcient.

70Mbps is too slow. There might be interference between those two adapters. Move it to a different outlet. And move away from high power appliances. It's hard to tell which appliance affect it, so...

Yes better pair one by one. And try the 1 second pair after the 10 second pair. You can follow the video http://www.tp-link.com/en/download/TL-WPA4226KIT.html

Is your usb stick listed as compatible? If not, last thing you you can try is to make a bin file on your own, http://www.tp-link.com/resources/download/TP-LINK_3G_USBSniffer_Guide_105.zip

Is there any error message when you connect the Z2 phone to the tplink wifi? Have you ever changed any wireless settings, such as network name, security type or channel? If not, I would suggest you...

Do you install the latest firmware? If tplink support cannot fix it, maybe get a replacement.