I think 2 hours is probably fine if there are no delays. DL uses a mix of regional and mainline on this route. I think landing at the far end of T4 vs. T2 is a wash given the landside transfer you'd have to make from T2 to T4 (I would probably just walk and not bother with the Airtrain), and your bags will probably be out at T4 by the time you get to baggage claim. (Though, FWIW, JFK is the *only* place where DL has not met its 20-minute baggage delivery guarantee for me -- I think more often than not I claim the miles.)
That said, if there is any ATC congestion, this route is most likely to be delayed as it's apparently rather difficult to slot the planes into the flow heading into NYC since it's so close to NYC.
So as others have said, it's probably too risky. The 4 hour connection should be fine, and if you're on time you should have time for a quick visit to the TWA hotel!
Plus with 4 hours, if there is some issue getting into JFK you can at least try to get a flight to LGA as a backup; they run hourly (at least on weekdays). Making that transfer (by taxi) is obviously not ideal, but with 3-4 hours it's totally doable.