With a PhD from Northwestern, I believe that it is easy for you to get an assistant professor position in Hong Kong. You can see some of the faculty member of the Chinese University of Hong Kong is from Northwestern University.
By the way, I would like to ask the background of LZ, such as GMAT, GPA, Bachelor and Master (mainland or US) Any research experience or publication?
I see. That's why. Your background is very strong, GRE V700 + Q800 already very high
You had experience with northwestern to do research. It is a very important thing. I think you should have other offers from top school such as MIT and Harvard too.
Math bachelor will help a lot. Actually, in my humble opinion, studying for Bachelor and Master in Business are not competitive for PhD in business. People can take CPA to learn business and accounting knowledge but Math, Econ and Stat major are very competitiive for PhD application.