Eich, FSX isn't my game- I'm still big into FS2002 and FS2004 (FS9). To be honest, I didn't know FSX had issues on modern systems.
You may want to check out:
https://www.sim-outhouse.com/sohforums/content.php
There's still plenty of FSX traffic on the forums and it would be a great place to find the answers..

I hang out in the FS2004/FS2002 forum.
Here's a typical thread from some know-it-all in Iowa:
https://www.sim-outhouse.com/sohforu...e-for-zswobbie)