Originally Posted by
jason8612
... this time I have to be in early in the AM at port to get the car

Why not follow the advise from oliver2002 and take a rental car?
"early AM"! From HAM to train station to Bremen to Bremerhaven, my guess would be 4 hours. From BRE to Bremen Hbf to Bremerhaven 2 hours.
However, to go by rental car is also no fun:
-HAM - Autobahn - Elbtunnel (should be free early AM) - Autobahn Bremen, Bremerhaven, my guess 3 hours.
-BRE - through the city of Bremen, pass Weser river - Autobahn to Bremerhaven, my guess 2 hours.