Stilllearning is giving you sound advice.
I am a Realtor and do my best to avoid ugly divorce situations. So often, too often, one of the parties does not want to sell and it shows.
So often, too often, it becomes impossible to get the two parties to agree to anything.
An appraisal is nothing more than one person's opinion of value, at a precise moment in time. Given the current market conditions, in most places, in the U.S., you are more than likely chasing a down market. Add an addict and a divorce to this mix and it can become impossible. These things can and often do drag on for years.
If he wants the house, and is ready and willing to pay 1/2 the appraised value, take the money and run.