Therefore, thanks TargetMaster, but me and my salt will stay here.
Your frustration is noted, I share it to be clear, but it need not drift away from the topic to get your point across.
I have nothing new to report on this, however, it would be prudent to remove all DLC (uncheck in Steam) for all players, no MODs, not user-created races or ships, just the absolute vanilla game.
Also, and prior to any test, this dir should be renamed so the game, upon 1st start, can recreate it in a default state (do not edit any settings prior to the test):
Or any other dir that has to do with GC3, again, rename it so the game can create a new one once run.
If it runs well for MP, add one DLC at a time to see what one causes you issues.
Stardock Support Manager