Not a lawyer, but my parents were RE brokers. Back in the day, you only owed an agent the commission if they showed you the house or brought the listing to your attention (back then, they just had these huge MLS notebooks — no public listings).
IMHO, you owe him absolutely nothing. OTOH, it would be nice for you to pay him for his time…maybe $500-$1,000 like the OP said. Unfortunately, with his attitude and totally false claim about you owing him the commission (based on what you’ve said), I’m not sure he deserves anything at all.
