Try to login the router's web interface when it disconnects. If you cannot, check IP address, default gateway obtained on the laptop. Probably you should upgrade firmware of TL-WR702N. By the way,...

I think hard reset is the only method...

Try to modify some wireless settings, like channel to 1, 6 or 11. By the way, any other wireless clients are working OK? Update the driver of wireless card on your computer.

Not sure. If you didn't install utility for Windows 8 on their webiste, it is worth to try.

Try MAC Clone and change MTU size to 1440 or 1400 on its web page.

Is it public IP address obtained in 3G/4G section. Just try to follow the instruction below to do the settings on the router : 1. Configure a static IP address for the PC need to be waked, for...