The fact that your H claims to have had a normal childhood could easily just be denial--certainly, my H, even if he (rarely) mentioned an incident in which his mother sounded abusive, would insist that their relationship hadn't affected him negatively. Yet, her death caused his MLC, which ended when he was finally able to confront her abuse and control.
It sounds as though there are a lot of potential triggers for an MLC based on a lack of parental nurturing for your H--his father was likely depressed and therefore unavailable, and his mother's decision to remarry may have felt like abandonment. Because children tend to blame themselves for whatever goes wrong, your H probably retains feelings of guilt.
Funny, but a lot of the things you mention were shared by my H--being in an incubator at birth, witnessing a death as a child, not coping if I raised my voice (his mom pinned her anger on him), as well as the lack of personal emotion, hypochondria and fear of death. The last are all, as I'm sure you're aware, symptoms of depression.
Has your H ever been treated for depression? Is there a possible genetic component, as you believe his dad was also depressed? Do you feel that he was not depressed when you first met?
As to why he is so damaged, what do they say--95% of families are dysfunctional? We are all wounded, in greater or lesser ways, by our childhood experiences. In order to fully grow up, we have at some point to examine ourselves, fully and fearlessly. The odd thing is, it's such a painful and terrifying thing to do ... and yet afterwards, we're left wondering, what was so scary about that? Most of your H's "damage," at this point, is that he somehow feels that he failed when he was a child, which has crippled his self-esteem, and he does not feel brave enough to confront the origins of those negative feelings. That doesn't mean that he couldn't, at some point.
In the meantime, you will feel better if you can take your focus away from the (for you) unsolveable puzzle of your H and place it back on yourself. I found that things didn't improve until I forced myself to identify and face my greatest fears. For example, I visualized exactly what life without my H would be like, aspect by aspect--first I could hardly force myself to entertain the idea, and then I relaxed in the knowledge that I could flourish. What are your greatest fears?
