The marriage has to end before there is any chance to rebuild a relationship. The only strategy to be concerned with now is how to get finances and legal matters taken care of. He should not be doing this separation or possible divorce filing as a "final last resort" strategy. This is for Frank and his kids survival emotionally and financially.
I do think that Frank was just kidding in his remark - he was just being sarcastic that he thinks she is going to try to weasel her way back because of her cake eating nature.
