On the whole this looks possible. However, I think the one thing that might be held against you is that you are a math major but did not get 800 on the GRE. Is it possible to retake it and get 800? Can you think of anyone who could write you a stronger third letter? If you are in the chicago area it is not too late to offer to assist a marketing/ob professor with their research for free in an effort in impressing them.