keep the job, study for the GMAT on the side and take as many math classes as you can. you dont need teaching experience to get in to a phd program...the math classes are for your benefit more than anything. youll either take them before you start or you would have take them during the phd rogram to catch up.

also, be aware that even a perfect application may not get you in to a phd program. i graduated with highest honors from an ivy league school, 4 years at big 4 (tax) and 99th percentile on my GMAT and did not get in to my phd program of choice. i even had conducted pretty hardcore statistical research for an accounting research class i took right before i applied, wrote a big research report outlining my findings (that my prof used as a springboard for his own published research) and sent that in with my application. i was not one of the 2 people that got in to the program i applied to that year. i'm not trying to dissuade you, just want you to know the reality is that spots at these top programs are insanely competitive. my best advice would be to start talking to people at these departments - profs, advisors, admissions people, deans.., whatever... they'll give you advice on how to approach the app and what they're looking for, and they might give you an idea of what being in an accounting phd program is really like.