I might try CH 8 then 11, even though there is someone on 11, it's a low signal.
I might try to lower the power output of the radio from High to Low.
Try disabling Short GI.
Other than this, not much else you can do. I would research some 5GHz information on Dlink model wifi adapters like DWA-160 (USB) and DAP-1533, 1525, 1522 or 1360(LAN and Wifi) as a 5Ghz alternative to getting away from this congested 2.4Ghz area.
Let us know how it goes.