New answers tagged the-others
Let's start from your second question: why is he there? Obviously, to increase the eerie factor and to further convince the audience that Grace and her children have a haunted house problem at hand. Now, in the context of the movie, which I believe is what you want to know, I don't think it is ever explained how this whole ghost thing works, so I can only ...
I would think so as the car that family moving in are driving are 1930s (I think it's Christler Duesenberg). Husband going and not comming back from second world war (1939-1945) and them knowing that war is over, would imply that it's around 1945+. This then makes it probable that she indeed died only a while ago.
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