2- I am not sure if this is a bug but the description said the Dread lords will not try to colonize new worlds but they were using transport ships to conquer colonized ones. They conquered a total of 4 worlds. Maybe they are supposed to capture but not colonize so I'm not sure if this is a bug or not.
Correct-not a bug. Colonizing and invading are nowhere near the same thing.
3- Probably not a bug but the level was impossibly difficult and if it wasn't for the fact that the Dread lords were not actively trying to annihilate all other civs, there was no chance to beat them. Even as I conquered their last planet, they had probably 10 times my military power
Also not a bug. They're supposed to be insanely difficult. 
Can't help you on the others, as I haven't played the campaign in ages-the video issue sounds like someone forgot to set it specific to the DL campaign (hint hint SD), while the non-completion issue has a thread or two on it...hopefully someone will stop by and tell you how they got it to work.