Skip the "ex wife" part.
Even though it's a joke, it potentially makes you sound bitter... And it loses some of the playfulness.
I fine-tuned that Number Close to basically being perfect / foolproof. Using it exactly like I showed you will give you the best results. But there's never anything wrong with experimenting & taking ideas & giving them a twist.
But I would definitely leave out the ex wife comment.
Its unnecessary & could work against you more often than not.