A married midlifer may feel their marriage is the cause of their growing dispair and their spouse becomes the target of their anger and frustration as the unhappiness within them consumes them. If they can get away from this person, if they can replace this person with someone who is more understanding, more comforting, then they can escape the unhappiness and pain.
For an alcoholic midlife crisis is even worse. I know mine resented his sobriety on me and then part of it was midlife crisis too. Either way was hell.
Sorry for the pain he is putting you thru, however, suffering is optional.