You can take charge of the money situation by giving him an allowance. Yes, take away his debit card. The traditional way would be for you to go to the ATM each week, withdraw a predetermined amount of cash for him spend, and when it is spent, that’s it.
There is also a way to automate this. Open a new checking account just for him (if your current bank won’t do this or wants to charge a fee, online banks may offer free checking with a debit card, depending on what country you are in). Set up an automatic transfer from your main account to his account every week or every two weeks. He can spend that and no more. Make sure he and you both understand that he cannot access the main account for any reason, but he can spend the money in his account however he wishes.