Yea, assuming the routing is legit (more experienced people can speak to that), you'd price out at the round business price (125k).
I don't think the last segment doesn't make sense to book now. Here's why:
You'd be paying an additive 40k (rather than just an extra 15k for the difference between a 25k domestic saver and 40k domestic medium). IE you'd be spending the price of a round trip domestic medium, to buy a single domestic leg. The total would then be 165k instead of 125k.
Depending on when you get to JFK, either book the JFK-BWI 7:30p-9:02p in econ (followed by a MARC train or B30 bus), or position using Avios (either if/when avail opens, or book an LGA/DCA for 9/20 morning), or take Amtrak/bus, or wait until 2015 and book a one-way medium (tier 3?) for 20k.
As for why the itinerary is pricing out at over the expected 165k, that might have to do with the fact that the current code on Delta.com (and on the phone agents' system) doesn't do free stop-overs anymore. That should add 25k since it's a within-Europe business saver. Why is it adding 47.5k? Not sure!