Wasn't it mentioned somewhere that VOY could draw power from Nebula matter and energies given off by stars? That's standard sci-fi power-generation stuff.
As for the Maquis thing, they really had no reason to be so dead-set against each other since the only reasons they were fighting to begin with were back in the Alpha Quadrant, not in the Delta Quadrant. What's the point of continuing to fight over things that don't have meaning anymore?
They never really specified what Neelix was there for, since they really didn't need supplies. It was a guide they needed.