If they came to our store & we knew the circumstances, we'd deny the discount. If they persisted, we'd call the ETL or AP. You could include it in the divorce decree that he surrender the discount card as he will no longer be a dependent. Otherwise, he could pass it around to his family & buddies to use at stores that don't know him or you.
If your divorce is final, it will cost you money to have this stipulated. If it is not, have it added into the divorce stipulation. If your divorce is final and the spouse refuses to surrender the card, I would contact corporate team member services and report the situation. They may be able to issue you a new employee number or advise you on how to best handle this. You'd be covering yourself, though, in the event of any repercussions since "your call may be monitored".