When should the dealer push the chips to the winning player

[psandman]

not necessarily. Your initial question was when should the dealer push the pot.

Now you ask what happens when he does it wrong. Part of this answer will depend on when you speak up and if it can be confirmed that you in fact had the winner. (If the dealer has destroyed the board you don't get to win the pot just cause you claim to have a winner.

You need to speak up immediately don't wait for the dealer to psuh the pot destroy the board and then speak up. Say ething as soon as the pot starts going the wrong way. If you delay you have to share responsibility for the mistake.