Have you tried to clone MAC address? Connect modem to WAN port of WR740N by cable and connect the sony laptop to one of its LAN ports by cable connection as well. On web interface of WR740, go to...

D7 is used to replace the 940N(RT)? If so, D7 is configured in wireless router mode?

Upgrade the latest firmware. If it won't work, try to change some wireless settings. #5 and #7 mentioned what you can try...

You'd better test to see if to disable 5GHz helps or not... You can try different channels like 1 6 or 11 and you can also try channel width 20MHz. If none of above settings work, you may need a...

According to its specifiations, cannot. http://www.tp-link.com/en/products/details/cat-9_Archer-C8.html#specifications Support Samba(Storage)/FTP Server/Media Server/Printer Server

You have to open ports for the IP address of the PC which needs to be waken up. Some users provide some configuration suggestions here....