KDFW is probably one of our best performing sceneries, and it should run better than KJFK. Since it's uses the video card more than JFK, it's likely your problem is a video card setting.
Of course, with such large airport, if you have 200 AI, the low fps is obviously not caused by KDFW, it would be just as low with the default scenery so, first test without AI, and if it's still low, then you are sure it's a problem of your configuration.