Stop making a big complicated issue about this.
We all telling you what to do. And it is very simple:
Either you pay them what they are asking and your dad get the apartment he wants.
Or you get a new agent that that start a new research and you get something else.
Since the broker, your father hired is the one who contact the listing broker for your father, well the listing broker can't do rent to your father without your father's original broker. That's a fine and a possible license revoking at the REBNY. I'm sure he wouldn't risk that just for $2200.
Your father's original broker did his job by finding your father the apartment he is looking for. Without him, you or your father would struggle by yourself to find that specific good deal or will never find. So he deserved his broker fee.
Now the only mistake he made is by not disclosing exactly how the deal will go in case there is two brokers involved. Either he did, or you or your father didn't understand, well, it still go one way: your choice (you are the client).
Now choose to make a decision that will prevent you from not finding a deal like that. I don't know you or your father, but if you have a place for him to live at right now until he find an apartment, well it is up to both of you. If he is in the rush to move-in, just go ahead and rent it, pay the broker fees they are asking and make sure to never refer them to anybody you know.
If your father is not in the rush and you are willing to take the risk of never finding that kind of deal again, well take another broker and this time, listen carefully and ask all questions before starting working with them.
If you need more advices, you can contact me directly at email@example.com
Global Market Specialist
(o): 212.252.8772 (EXT.782)
(c): 347.593.9319 (Temporary)