I flew with Delta, and at the time their limit was actually 5 kg (11 pounds).
If you are significantly over the limit, I would really recommend booking him in cargo, that way you will at least be sure that you both get on the plane. Otherwise you might not even be allowed to board at all and lose the money.
There is no law about constantly bugging a stewardess at every plane change to confirm that your dog is on board, otherwise you simply refuse to board yourself. They have walky-talky contact to the baggage handlers, so they can get up-to-date information at any time.
Follow Redyre's advice for securing and labeling the crate and it should really be fine.