Your problem doesn't have anything to do with the installation of KLAX, which is correct, and doesn't have anything to do with antivirus, etc. You have both the Addon Manager menu and Couatl running and you have the scenery, although it's missing some part, but this clearly indicates everything is running fine, there are no installation problems.
Putting all settings to minimal, also, is not a very good idea, there are bugs in FSX that objects disappear if you turn the Autogen entirely off.
Also, you should first try using *everything* at default on the video card. Something in your screenshot doesn't look right: you have the card set for 8x antialiasing and 16x anisotropic filter, which should give you a very good graphic quality, but your screenshots are really bad, with no antialiasing and no anisotropic at all, so it seems something is wrong with the video settings.
If you are sure you don't have FSX in any of the Compatibility modes (which causes problems with part of buildings disappearing), since the programs are running correctly, it can only be something wrong in your system installation that is affecting the video card, if you can't find it, a Windows reinstall will surely fix it.