@ChubbyPanda a month and a half should be enough time to study to bring up your English ACT score.
Do you know which of your 3 private schools you want to apply to? WashU loves their students to show demonstrated interest. Attending school fairs, contacting your regional rep, and visiting are some ways of demonstrating interest. If any one of Georgetown, Northwestern, or WashU are high on your list, you should consider ED.