Dear Sir, My settings are correct including Anisotropic settings at 16x
No, they aren't. Your screenshot clearly indicate you have Antisotropic filtering disabled in FSX. Perhaps you are looking at the Global settings of your video card, but if you have a profile for FSX, or you used a 3rd party enhancer, you must check the custom FSX profile, and/or the 3rd party enhancer tweaks.
Also, try different Antisotropic settings in FSX itself, when the driver is set to enhance the application, you might get better result by turning it off in FSX. But try BOTH settings.
And of course, be sure you have the textures slider in FSX to the Maximum value or, better, use the Addon Manager to set HD texture, although KDFW doesn't use them.
I'm only trying to find a fix as all your other add on airports are working great.
Not all of them have custom runway textures, and ONLY those that have, are affected by the lack of Anisotropic filtering. There's nothing wrong with the scenery, your screenshot is a clear case example of lack of Anisotropic filtering.
Clear proof of this, is your FIRST screenshot, which shows also the *default* scenery around KDFW, and the texture quality is just as bad as the runway, and the same is true for the airplane textures, they are blurred too.
Do you use the "Fiber Accelerator" program ? If yes, perhaps that one is playing tricks of you and in order to keep the fps as requested, is lowering your setting in real-time.