Thank you, this helps a lot! My grad GPA is 4.23 on the scale of 4.3, so I think the problem is on my GRE or writing sample (or both). And I am kind of surprised that you think my AW is not a big deal comparing to my Verbal. Can you explain a little bit more why you think it is less important? Because it may affect the way I prepare for GRE. To be honest, I have spent a lot of time practicing AW, but I still only got 3. If AW is not so important, I will spend my time studying Verbal.
As to the writing sample, I really appreciate your willingness to help read my sample. But I am not familiar with how this forum runs, should I PM you, or attach my sample in the post?