I also can't get the hang of the campaign mode.
The DL campian isn't as good as the sand box mode. You may wish to play sand box instead if you are not enjoying the campian mode.
My problem is that unlike Imperium Galactica, Dread Lords doesn't have a very effective way of keeping moral up. It seems that after a while moral just drops to 40% no matter what you've built on the planet...
Morale gets worse the larger your population gets. Its at its worst at 25 bil where its almost impossible to keep them happy. Any population size after 25 bil is just as bad. For those reasons, you don't want to develop your population more than 20 bil... if you dare to develop that far.
The reason why you want large population sizes is because it helps to protect your worlds, and to provide a taxable population base. The taxable population base is equal to the square root of your population, so its a game of diminishing returns. Paying for the resources to maintain absurdly large populations isn't economically justifiable after a while, generally the case after 20 bil.
I'm on the third part of the campaign where I have to take over the planet in the upper left corner while not letting the newly released Dread Lords take over my planets.
You may wish to recheck where the upper left corner is.
The minimap is tilted counter clock wise 45 degrees, instead of 45 degrees clock wise. As such, you should be looking at the left corner of the minimap, as opposed to the top corner. I didn't realise it the first time I played that map, so I ended up eventually figuring out how to beat up the Dread Lords, conquor their planet, and then I spent some time wondering why I hadn't won the map yet. In reality, I had conquored the planet in the upper right corner, completely ignoring the one in the upper left corner that I should of been going after.
Not a total loss for me though. What I learned from that mistake helped to make me quite proficient in beating up the Dread Lords.