I've had American pull this crap with us in the past, but never with Delta. When did you book the flights originally? If it was within the past 60 days I would suggest contacting your credit card company and seek full compensation through them. Once settled, I would rebook with Jet Blue to-and-from SXM out of either Boston or JFK. Jet Blue usually sticks to their schedules fairly well, and when flight changes are made they are usually insignificant. Good luck.