I think your scores are your biggest weakness; improving those will greatly improve your chances. The only other advice I have is to make sure you are developing great relationships with the teachers you’ll be asking for recommendations. Also, spend a lot of time on the essays and make sure that they stand out and tell admissions officers something about you that cannot be ascertained from your list of EC’s and awards. For example, you could write about how your passion for solving problems (i.e rubies cubes and playing chess) relates to your intended major (engineering).