When building the tracks, I've been using the trains from our stash behind the screen instead of from the general supply. The game seems to work fine like that. How different is it to play it correctly?
You just invented a completely different game.
I don't want to sound mean (sorry), but this is the funniest rules-mistake I've ever read. You might as well have the player with the least money/points win at the end of the game.