Here's the course.
http://as1.wdpromedia.com/media/rund...alf_Course.pdf
All street closures will be in place by 5am, with some starting at midnight. In my opinion, you need to leave before 5am because Harbor will likely be closed. 5:45 is cutting it way too close with Harbor being mile 3. Also, if you plan to use an airport shuttle or taxi there is a very good chance that they will not be allowed to go to your hotel, and that only cars on Harbor will be allowed to leave. You should consider moving to a hotel outside the race course the night before, if at all possible.