Flight leaves at 5:00am. Is the rental company have someone at the desk to check my rental in earlier than when I rented it?

Yes, just drive around the loop till you find your rental company which is well marked and pull in and there has as been someone there to check the car in.

Yes

Yes It is very Confusing to maneuver there. So Start early if you can I had to get to National Regan airport by a certain time of course.