Hnla, I'm back again. Every time I log in, I think about your issue.....which I see does not seem to be progressing.
So, How about taking your FSX system back to basic. Remove, or disable FSUIPC, any weather, (including clouds) any traffic, any other sceneries, GSX etc, and BGL's you may have created. Also, disable the FSX.cfg, so that FSX builds a new cfg file when it starts.(you should put in the HIGHMEMFIX=1 in [GRAPHICS] fix into the new cfg file) Remove all monitors, (ummm skippy, four screens!!!)other than one. So when you fire up FSX, it is if you had just loaded FSX from new in 2006.
Now, if you do not already have it, download this scenery editor,
https://sourceforge.net/projects/fs-sceditor/ It is now version 1.17
Load it and you can actually see what scenery is loading in FSX. Use the 'List' tab, you can see which scenery(s) are loading into FSX. You can de-tick all the third party scenery to NOT load, so that when you fire up FSX, only stock airports and sceneries you left selected, loads. This neat little program also indicates if there are any scenery errors.
Just to make sure it all works, fire up FSX, choose a stock a/c, and load into any non third party airport like KLAX. Do a circuit. All fine? Great, your FSX system works as intended. Close FSX.
Open the Scenery Config Editor and select KMEM. Save file. Now fire up FSX. From splash screen, select KMEM, active runway. Use a stock a/c(trying to make sure memory is always conserved) If you can get to KMEM ok, do a circuit or two. NOW, if this works for several flights, load a PMDG a/c..it will give the memory a bit of a work out, see if this is ok. If so, you need to introduce the items you disabled one by one, making sure you close FSX. Sooner or later, you may experience the crash again after installing one of the add ons
Anyway, a long winded way to say go back to basic config and sort of creep up on your crashes. Probably by now, many people have purchased KMEM and are using it, proving it does work, you just have to figure out what is causing FSX to crash with KMEM.