You’ve done nothing wrong at all. You’ve shown great courage and empathy towards him and his parents. What you did was humane.
Having said that, alcoholism is a disease that makes the alcoholic behave in very selfish and sly ways. They crave the alcohol so much that they will lie, steal and anything else to get the drink. They use people. He’s used you and if you allow him to come near you, he’ll use you again.
He may be out on the steets, he may be out cold somewhere on a park bench. You’re not responsible for him. His parents have had this problem with him for years and they’re so tired of it... you’re enabling them to use you. They would love nothing more than for you to take in their son and care for him... to take over the enabling and give them some time off from the endless drama he’s created. I wish one of my son’s girlfriends would have done that too.
Not only is the alcoholic using you. His parents have an agenda too. Be aware of this and for your own sake, don’t make him your problem. Forget about him and don’t speak to his parents again. Keep away.... you’ve been a saint, now stop it.