No, it doesn't hurt to be Asian. I don't think race is really an issue for PhD.
You are not too old. I'm 45, and I'm not the oldest PhD student at my school. Age can play a role in the process, not because of some valid concerns. You need to convince the schools about the reasons you would be willing to sacrifice a lucrative career after your MBA to live the hard life of a PhD student, for example.
The GMAT score is going to be really helpful. Undergrad with math and economics too.
Work experience is usually of little importance for PhD applications.
About your experience with research from past jobs. Be very careful about that in your application. It can help, but it can also backfire. Probably some parts of that experience can be useful. But if the schools feel that you are interested in research in industry instead of academia, that can be considered a red flag. Another potential red flag if they feel you don't really understand the differences between the research you have done and academic research.
Right now, I think there are two things you can do to make your profile stronger: getting some kind of research experience and getting strong letters of recommendation.
Since you will work as a TA, that can be the perfect opportunity. Try to get close to at least 3 professors who are actively doing research and show your interests, skills etc., since you will need 3 letters attesting to your potential as a researcher (not a student or an employee). See if you can help in their research in some way, from small stuff like organizing data to big deals like being a co-author in a good paper.
If you can get strong recommendations from 3 professors, and at least some level of research experience, your profile will have no major weaknesses that I can see.
Then, it is a matter of defining your research interests and selecting schools wisely. If you do that, I think it's almost sure you can get into a very good school.