I know depression can be part of a MLC...it just sounded like classic D to me...again mostly because of the withdrawal from everyone...actually he stays closest to you, which is interesting.
My college boyfriend, which was a very very deep R in my life, suffered from terrible depression. He would go through these same phases. It was very hard. This all sounds so familiar. My heart goes out to you. The boyfriend wasn't my husband so eventually I gave up on that R. But I understand some of what you're going through.
I have often wondered about this, about this personality type, if there really are people who do require periods of "solitude" when they can't cope with other people, especially loving people it seems. And yet they will have periods when they seek connection with you. And what does one do if one loves such a person? I was intrigued by your description of your relationship and having no labels, etc. That struck a chord from my past.
Anyway...you're in my thoughts and prayers. You seem to have an innate intuitive understanding of your H...I pray that takes you both where you need to be, and if it doesn't, that you find your own peace in dealing with this.