Then I slowly introduced all of my addons, being the last 3 KJFKV2 KLAX and GSX, to find out that my NGX is not loading again. From the event viewer the error that I constantly get is a MSVCR100.DLL.
The problem doesn't have anything to do with GSX. Yes, of course it looks like that (because it's gone if you remove it), but the real issue is not CAUSED by GSX. It's caused by a conflict between VC++ libraries.
After unistalling the Couati addon manager the NGX comes back alive and if I reinstall it goes dead again.
What happens if you remove PMDG and leave everything else, including GSX ? I'm sure it will work so, this could be claimed as "proof" the culprit is PMDG as well, but I'm not saying that. The real issue is the conflict between the VC++ libraries.
The MSVCR100.DLL (Visual Studio 2010 runtimes), which is the thing that crashes, is used ONLY by the PMDG so, it's the PMDG that is crashing, not GSX.
We don't use the Visual Studio 2010 runtimes in any of our software. Following recommendation from Lockheed Martin (which suggest to use ONLY Visual Studio 2013 libraries), and considering the latest FSX version also uses the Visual Studio 2013 runtime library, we only use that one, nothing in our code has any relationship with the Visual Studio 2010.
By using several different versions of the runtime redistributable, chances for conflicts increase, so I guess this is your case.
It's not a normal situation: there's no *known* conflict between GSX and the NGX so, even if it would be best if they used the 2013 runtimes too, it's not usually a problem so, it's something specific to your system.
The only possible solutions is trying to uninstall everything related to Visual Studio 2010 runtimes, then download them again from Microsoft and reinstall them all.
Uninstall EVERY version of the Visual Studio 2010 runtimes, and download and install BOTH the x64 AND the x86 version of the libraries.