Sometimes it's best just to say, "You are a smart guy. Your wife is a smart lady. I am sure you, your wife and the doctors will find the answers you are looking for together."
And maybe hand him a schedule for support group meetings like alanon. Maybe you should consider attending one as well for your own information.
You didn't cause her addiction. You can't control her addiction. You can't cure her addiction.
And neither can he...