Hm-m-m-m... well... honestly I don't know the answer to this. Off-hand I don't know why you should not offer mid-life crisis as a possible reason for some of what your hubby is going through. He may or may not accept it. He may become defensive. He may get mad. But, at least based on the observations you described in your post, it seems reasonable to me.
I recall having replied to your introductory post where you mentioned your husband's loss of faith. And I know I gave you links to some articles, from PC's archives, on that subject. Here are links to 3 articles on depression in men as well as 3 on the concept of the male mid-life crisis. Also included are links to 4 articles on how to prepare to have a difficult conversation, 1 on how to talk to someone who always gets defensive, & 1 on the subject of stonewalling:
Depression in Men: It Looks Different Than You Might Think
10 Things You Should Know About Male Depression
12 Depression Busters for Men
The Male Midlife Crisis
The Mid-Life Crisis: An Opportunity in Disguise?
https://psychcentral.com/blog/when-m...actical-guide/
https://psychcentral.com/blog/tips-f...-tough-topics/
https://psychcentral.com/blog/5-ways...-conversation/
https://psychcentral.com/blog/how-to...conversations/
https://blogs.psychcentral.com/emoti...ficult-issues/
https://psychcentral.com/lib/how-to-...ets-defensive/
https://psychcentral.com/lib/stonewa...er-shuts-down/
My best wishes to you both...