To the first part, no. There isn't a schedule until they actually make it.
This year, the flights will cease on October 22nd with B6 1591 being the last JFK->ACK leg. The first flight was May 4th, 2018.
B6 594 is the DCA->ACK flight and began May 25th this year.
FYI you can just find all of this yourself on FlightAware.