I think your dad is a narcissistic alcoholic and I also think this isn't the first time he's stolen to feed his addiction. If he's willing to steal from his own son, and then have the audacity to say he deserves it, then he'll steal from you again once his partner stops enabling him.
That being said, short of putting all your money in a bank and hiding your debit card, there's not a great deal you can do. You can report it to the police, but a father-in-law dispute over a fiver isn't going to spark their interest that much.
Either way, he isn't in the right to do that. Regardless of whether people think you should be giving your dad money because he's your dad, it's your prerogative. He doesn't have a right to steal from you just because you're his son.