I have a different take on it. Pointing out the mistake causes the pitboss to get involved,and now a minor error disrupts the game,points out to the pitboss that the dealer is either inept or was daydreaming,and perhaps gets the attention of the eye in the sky.Little good has come from you being a nice guy.I'd let it slide.... unless its a mistake thats not in your favor.
As for can the house force you to repay the money- I don't really know,but there was a story that made the rounds a few years ago where Pete Rose got paid way too much money on a sports bet,and after they caught it,he refused to give the money back,even though it meant that several people would get fired for the mistake.That part of the story made the papers.What transpired later,if there was a court case,whatever,I don't know.
I have counted to infinity. Twice