Maybe he is confused about HOW to work in the marriage?
I think sometimes (myself included!) when you just don't know what to say or do you either turn to humor or sarcasm. I am not saying that is healthy but sometimes people just think a joke or a smart ass remark will sort of ease some tension.
This will be a slow process and I think that is okay. When you lose a parent it is very odd (and of course sad) because you sort of realize you are the adult now. Not that you were not an adult before but the person (parent) that was always the adult there is not. I am not articulating this well.
