This isn't about whether the father is right or not. This is about the father trying to save the future of his son. A male child who is living with his parents and is into gambling may still be less than eighteen and that is underaged betting. Imagine if this boy starts gambling at this age what belongs of him and his future. He should be out there learning a skill or acquiring some education that will improve his odds at succeeding in life and not the meagre money he has won from sports betting.
The only reason the child was out gambling is because the father isn't financially strong so as the child came back with such money, why didn't the father use the money to further the childs education. He would had punished him by not allowing him to have access to the money.
There are different ways to handle this situation, he could have also given the child some conditions before he can have access to the money. Like he should finish university, get a good grade or he won't have access to the money. He could have turned the money into a will.
He wouldn't used the money so the boy will understand the message from the father but not to throw away that huge amount. What if that was how God wanted to secure the boys future and that of the family. If betting isn't against their religion he shouldn't have rejected the money.