Prepar3D.exe crashing into ntdll.dll doesn't seem to be related to GSX.
That looks like a general memory allocation problem: fact it happens when you start GSX, might simply due to the fact you were already very close to memory exhaustion, due to the combination of scenery and airplane used, so when GSX ask the sim to create its own objects, they just don't fit in memory.
Prepar3D should never, ever, run into any Compatibility mode. It's reduce performances (each and every filesystem call will be redirected on the fly, and the same for each and every registry read/write), and even video drivers will run in a lesser performing mode. It's possible the video drivers less performing mode might save some small bit of memory, just enough to save you from crashing.
From the subject thread, I guess this doesn't happen on other airports. Are you able to use the airport with a default airplane ? If yes, that might confirm it's just an issue of not enough memory, because the combination of the scenery+airplane is taking too much.