My understanding is that Northwestern defers a very small (1-2%) number of ED applications. So you can’t expect a second chance with your ED application – to mean if you’re not accepted then expect a rejection. You’re right about the value of applying ED. Nearly 1/2 of the Northwestern class is picked during this round. This said, a stellar application will help during RD. So I recommend you aim for that. Your other scores suggest that with preparation you can bring up the SAT 2 scores significantly.