I can understand trying to avoid the early morning flight. I usually do this by hopping back to AMS the night before my return to the states. If the layover is less than 24 hours on international flights then it's the same price for the flight. Doing this helps break up the return plus you get an evening to spend in AMS for free. Just something else you might consider. NW AMS-DTW flies a lot of A330's...it's a nice ride and even in Coach you've got IFE at your seat.

Have a great trip!

Tracy