big questions

Q: if my engine is rated at two pounds pulling power how can it pull all my cars that i know have a combined weight of over 2 pounds.

A: Two pounds pulling power means it could pull a brick weighing 2 lbs and the brick would move (not very elegantly though).  Note: Bricks dont' have wheels.  If the wheels on all your cars had zero friction, you could theoretically pull an infinite number of them.  But alas, there is always some amount of friction in the wheels rubbing against the track.  So the combined engineering value of all that friction could get as high as just under 2 lbs of force and the engine could still move pulling those cars.  An engineering problem worth thinking about, eh?