From what you describe it does sound like the classical symptoms of a mid life crisis which manifests as depression. I would recommend the use of Cognitive Behavioral Therapy. In CBT, one is taught new ways of thinking and behaving and as a result, one's mood improves. anxiety decrease. In addition CBT is evidenced based as the most effective form of treating anxiety and depression.
Best wishes and good luck.
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I still think this is a factor of midlife crisis. I would suggest that you don't push and leave it open ended. Allow him some space. That does not guarantee a reconciliation, but if you push it, you are sure (in my opinion) to drive him further away. Good luck and try to be patient.
I don't think that would work in your interest at this time, maybe in a few weeks, but right now allow him the space that he is demonstrating that he wants.