I've been on NW planes where the FC NON-BULKHEAD seats fold up as well. I think all the non-bulkhead seats on the DC-9 fold up, both coach and FC. I would call NW and double check though.
Bulkheads DEFINATELY have more legroom. But the arms don't fold up. If you can, try to snag 6-D. It has unlimited legroom and no seat in front of it. Its still a "bulkhead" type seat that doesn't have a fold up armrest though.
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http://www.seatguru.com/ for seatmaps.