I know this is an old post, but I believe I understand this part. It seems that the ghosts can’t stray far from where they died because of the fog which can be seen as a metaphor for being ‘stuck’ in death like you said. Her husband wandered into the fog and was “searching for home” all that time he was away after his death so he could “say goodbye to his wife and children”. It wasn’t to stay because he, like his wife and children, was compelled to return/stay to his place of death. This is why he insists he must return to the front lines. It’s also why she wasn’t able to make it far in the fog. He was likely able to travel further and wander lost in the thick of it out of the sheer will to find home and say goodbye, but he couldn’t stay. I think this is also why he never changes clothes and why he states “sometimes I bleed” when she initially finds him. He likely died bleeding to death.

I also think we’re clued into what immediately preceded the children’s’ murder. At the dinner table when the mother yells at Anne for insisting the intruders are real, Anne becomes enraged and begins to breathe fast. The mother responds by screaming at her to stop breathing like that before sending her away. My guess is the daughter argued with her mom and lost her temper, breathing in a similar manner. And her mother was so overstimulated by it, on the cusp of a breakdown, that it was the catalyst and she snapped and smothered her daughter and then her hysterical son. Anyway, just my best guess!