Two things:
1/ Use
inSIDDer, it is free, to get more info about the other networks that are suspected of causing interference.
Looks useful for this, but doesn't run on Mac, and I haven't yet reinstalled VMWare on the MacBook I'm currently using. I have a Windows desktop in the middle of the house, but it's highly immobile. I'll have to get around to getting Windows installed on the laptop this weekend.
2/ Crack open MSpaint so we can get a better idea of the house layout and it's wings.
That I can do. The green stars are the approximate location of the existing APs