I don't seem to remember that Reiko thought that her husband treated her badly or that she blamed him for anything. I thought that it was more like Reiko knew she was messed up and tried to warn her husband about herself. But I don't have the book in front of me right now, so I might be remembering things incorrectly.
As for the last scene in the book, I don't think that it is meant to portray Watanabe's world spinning out of control. I think that it is supposed to contrast with a scene right near the beginning of the book. In that scene, Watanabe is remembering one time that he and Naoko were walking in a big field. The strange thing is that although he remembers background details like the field and the sky quite vividly, he can't picture himself or Naoko in it, although he is sure they were there together. So, I think this contrasts with the last scene, where the background is entirely lost to him. Instead, he is only focused on himself and Midori. This is just a pet theory of mine.