I have to disagree with everybody here. Sounds like he derived his personal value from his business. He lost his confidence when he lost his business.
The key is for him to find his personal value again.
Then again, you say he used to have sex with you every night...when did it stop? when you got married, or when he lost his business?
Since you are not interested in leaving yet, I suggest:
-Sex therapist. Not some stoogy marriage counselor who only provides a stepping stone to divorce. Some members here have reported success with this.
-I do think you should be upfront with him: "You need to make love to your wife or you will lose her too"
Because, even though you say divorce is not an option, imagine yourself ten years in the future, having only had sex a dozen or so more times. You WILL end up in an affair or divorced.