Yes, it went all the way down to the south/eastern end of Canarsie Rd. See here:
http://rutlandtrail.org/mapview.cgi?lat ... e=Historic
or here:
http://rutlandtrail.org/gmap.cgi?NYnC-brooklyn.ny.track
I see several other interesting things comparing the modern and historical maps:
That there was a trolley paralleling the Rockaway Branch, on Rockaway Pkwy, heading up Rockaway Avenue to Linden Blvd.
That the route of the Belt Parkway in this area is entirely on filled land.
That the bent section of Avenue D (nearly north/south) is a fossil road which used to go up to Linden Blvd.
That there used to be farms between Flatbush and Canarsie just 100 years ago.
That St. Jude Place is also the remains of a north/south road.
Alas, nysubway.org has been taken over by a domain name spammer.