I have been trying to edit the main campaign too, trying to make my ships invincible. hehehe.
I have located the difficulty adjustments file set the Easy Setting to a -5.0 damage multiplier, so i don't get hurt.
It works in the standard Galactic Conquest, build times are accelerated and stuff like that and invulnerability works, but none of the changes work on the main campaign.
Where is the info that the Main Campaign draws the difficulty settings from??
EDIT: Well, i have tried everything i can, but i just can't get the file:
to affect the Story Campaign.
It works with the Normal Galactic Conquest, but thats it.