You will earn EQM on a Delta flight even if not a code-share. See http://www.nwa.com/worldperks/earn/airfl.shtml

Also, unless there is a reason for wanting to fly from JFK specifically, there is a non-stop CO flight from EWR, but be aware that lower fare buckets do not earn full (NW) EQM. If it just a connection (and not a stopover) in New York, you could also connect in ATL on DL.