Hi there,
Thanks for your post. Overall it sounds like you are on-target with your breakdown of the schools you are interested in; keep in mind the GMAT can play a decent role in what tier/level of school you'd have better chances at, so be sure to work hard on that GMAT prep! And looking at acceptance rates is one thing but be sure to look at the average GMAT scores of the schools too to get a better feel, for example I believe Michigan is higher average than USC part time. The other thing to consider is that many part-time program applicants have closer to 6 years of full time experience, so you may be in a position of having to justify why NOW makes sense for you vs gaining more experience. Finally, you'll want to narrow down your school list some since it is pretty time-consuming to create each application and tailor your essays etc.
Good luck to you!