I'm not in NYC but I did find this:
NYS DOS, Counsel's Office, Legal Memoranda, Apartment Hunting which comes from this site:
NYC Rent Guidelines Board
Seems there would be two things that would effect this...1. did you have anything in writing 2. even if the agreement was verbal, since he changed the terms of the 'contract' by moving the move in date back, if he earned his 'commission'. I would say no, but I'm not an attorney. The first link has a phone number on the bottom of it for the complain board...they should be able to answer those questions for you.
Good luck to you. You should just stay on Long Island..it's nicer.
(I used to live there)