Nice! Sorry I can't answer your question about the whistle.
For future reference in case someone else reads this thread... on THIS SPECIFIC LOCOMOTIVE you could have gotten away with the Miniatronics connectors because unless someone modfied your loco, the tether doesn't carry motor power-- just a little bit of current and back-EMF data for the sound board.
In other applications where the tender has pickup rollers that feed the motor, GRJ (as usual) is right, a heavier-duty connector is needed.