Dr. Giggles said:
Your score on the real MCAT, for whatever reason, can be substantially higher or lower than what you score on practice exams. I was scoring about in your range on practice exams but ended up in the high 30's, so anything can happen. The pressure of the actual exam can work both ways I think; the people who respond poorly to stress could improve the scaling for those who respond to it well.
However, you sound like your chances are excellent, probably better than 95% of applicants out there, but you shouldn't consider yourself a "shoo-in" anywhere. I bought into this mentality a year ago and thought I could get in anywhere with stellar numbers and mediocre ECs, clinical experience, late applications, and other things.
Again you sound like an outstanding applicant, but give every aspect of the process 100% until you have your first acceptance in your hand. Numbers are important, but if you think they alone can get you in, even to your state school, you could be in for a rude awakening.
You also might want to consider applying to Loyola, Southern Illinois, or Rosalind Franklin as backups. Medical College of Wisconsin and Wisconsin-Madison are also pretty close to Chicago. Just be sure to include a few backups in case things fall through at UIC; chances are, you'll come away impressed from at least one.