You must have some kind of inferiority complex because of where you go or something, because any advice you give on this forum is bias and half the time an exaggeration. Re read what you wrote and tell me if it makes sense.
Ross takes 1300 students a year and they are not all from top universities. And it is not a huge disadvantage if you from one of them. We are not talking about Yale or something who factor the school you went to and adjust your gpa. Ross dose not do that to your gpa.
To the OP, you do not have to go to DUKE or UMICH to do a post bac in undergrad to get into Ross. Ross does except community college credits, but if you can do the post bac at a small 4 yr state or city college, it would be better.
This is what i would do in your position. I would register for the sept mcat, probably the last day it is offered. I would also call ross and ask them if you applied for january and were rejected, could you still apply in sept of the same year with a new mcat and grades. If they say yes, i would apply now for january. I would not tell them that you are taking the mcat in sept (because they will hold for your new grades). I would try to have everything complete asap. Hopefully they will give you a decision by late august. If they offer you MERP, i would take it. Then your fate is in your hands, and you have to prove to them that you belong there. I wouldn't be shocked if they accept you but your chances are slim. It is better than paying and taking classes like g chem, orgo,etc over which have minimal benefit to you when you reach med school. At least MERP will help you 1st year
If they reject you and you really want to go to the big 3, then i would retake courses in the fall and take the mcat again in sept.Thats the benefit of applying now and trying to complete within a week. If you know your decision by the end of august, it easy to register for courses if needed. While you are waiting for a decision from ross, pretend you are rejected and just study for the mcat again.
If you are getting a 23-24 on your practice exams, just postpone it to january. No point getting the same score again. Apply again when you feel your have improved your app.