The replicated in the client is news to me, should not be that way To do any change, like SSID if you are on the AP side change first Client SSID then change AP in case you are on the Client side the...

http://www.tp-link.com/en/faq-289.html At the end if the tuto there is a note, that note should be in first line, do it before you start

You posted and you answered 5ghz is your solution, do not buy 7510 buy a pair of CPE510

Need to know why are placing a 3G/4G Wireless N Router TL-MR3420 and not a 300Mbps Multi-Function Wireless N Router like TL-WR842ND AP1-AP Mode AP2-Client Mode, here you are cabling from AP2 inside...

AP-Client router mode sucks cause is a repeating mode Set Client mode it's like laying a imaginary cable between devices, for wireless on Client side just add a cheap router as AP

AP Router mode has Mac clone under Network