I hate Repeating modes cause they suck, try WISP mode it's a repeating mode too here http://www.tp-link.de/article/?faqid=617
Set 192.168.3.0 as ip
Step 3 you can use the Quick Set Up or config manual
Step 5 set Dynamic, Ignore the ISP your main router is the ISP in your case
Step 7 in AP Setting set a dif. SSID from main router, later when all works you can set same SSID as main router, I don't recommend it, stay with dif. SSID
If you still got problems upgrade to the, Beta firmware and test, here http://forum.tp-link.com/showthread.php?79363-TL-WA7210N_V2_150127_Beta-add-support-for-MAXtream-(TDMA)-mode
And if you still got them, as I told you Repeater modes suck, instead of repeating send the wifi, set 72 on AP mode, mount 72 outside facing and tilting as need it, towards the area you need to extend wifi
and if does not accomplish your needs, cause does not cover all the area in need, just add a 741 router flashed with a third party firmware, and that will do.