Poor judgement and erratic behavior: Who to see?

A friend and her elderly (82) husband have gotten along well enough, though he's sometimes been controlling, verbally abusive, and drinks too much. He's retired military. They've been preparing to sell their home and move into senior living. Suddenly his behavior has become erratic. He's different in the morning than in the afternoon. He suddenly decided to divorce her and prepared the papers to file, offering her some money from the sale (house isn't communal property). He would move to another state, also leaving his beloved dog. Today he says he loves her and doesn't want a divorce, but in the same conversation talked about going down to the courthouse to proceed with the divorce filing. He's facing heart surgery soon, has been depressed and paranoid, and has considered suicide. Is it possible he's suddenly experiencing strokes, senility, or Alzheimers. Who should we see besides a divorce lawyer?