WDS repeating is good. But I'm strongly suggest you should use 2 Pcs of WA5210G Outdoor CPE on both your home and sister site.
Your sister site mode is should be AP (Access Point ) Mode and you are setting up to
WISP Client Router Mode ...
Im having a repeater problem with the 5210G
I even installed an tp-link external intenna set it up as a repeater and added a tp-link external omnidirectional antenna to the roof, getting 4 lights on the link but no signal being transmitted... repeated.
I wish I could talk all "techy" to you, but I have no clue about that. All I know is the folks at the 800# walked me through it. I do know that at first it wasn't working but then the person remember we had to go back into my computer and adjust the settings back to what they were before.
I'll admit, the instructions that came with the unit are crap, but I also found step by step instructions (after I had it working) by googling it. You may want to try that.