Agreed.. now I feel bad.
What I'm trying to get at is that the we need to know the make and model of the parts before we can really know what's going on. You need to get that information from the previous owner, otherwise it's going to be difficult to figure out what's going on without ripping everything apart and searching part numbers to figure out what you've got. It sounds to me like the previous owner screwed up the car, couldn't figure out how to fix it, so he decided to unload it on someone else.
I do think there is an issue with the clutch and/or flywheel. Any flywheel under 10-11lbs will most certainly cause problems, but that still does not explain the lights dimming and engine shutting off. The only reason the lights would dim would be because voltage in the electrical system is dropping. This shouldn't happen with a normally charged battery. It could be your alternator isn't charging the battery, it could be that the battery isn't holding a charge, or it could be a loose connection in the electrical system or a short.
The first thing I would do right now is take the car to a local auto parts store, like O'Riley's or Autozone and have them test your alternator and battery (they should do it for free). If that checks out fine then go on the hunt for loose connections starting with the main wires at the alternator and battery, then check all the connections that could have been messed up while changing the clutch.
Problems in your electrical system could easily cause the car to run rough, buck, and stall. And it kinda makes sense that it would get better as it revs up because the alternator is able to put out more juice at higher rpm.