Yeah, you probably found the ending a little abrupt. The Coen brothers did this in their last 3 movies. They like to leave the ending open and leave some place for the viewer to make their own hypothesis. They prefer to ask questions than to answer them. That is way more evident in A Serious Man. The whole movie turns around that idea of faith against chaos (as in theory of chaos).
yeah, in retrospect i guess i find it to be a legitimate ending that i can't really be mad about, it was just so unsatisfying!
edit: also, just watch Is Anyone There tonight. some random movie we saw at the movie store with michael caine as some old dying magician who makes friends with the little kid of the family who runs it. it was pretty decent, i enjoyed it.