You did everything you could. Like you said, he was a grown man and you could only make suggestions. It's not your fault.

My mom was sick my whole life. She had cancer. She couldn't do things other moms could because the medicine made her sick. She was in her bed a lot, sleeping away pain and medicine. She couldn't keep the house up and she couldn't take me to all the things she wanted. She she couldn't always be there for me when I needed her, because she was in bed. But, she wasn't a defective mom. She was the best mom ever! And I would not trade a single second of the time I had with her for anything.

So, you are not a defective mom. You were the best mom you could be! And it's not your fault! Sometime bad things happen. You got a great gift, those months he was your house buddy. The two of you were a gift for each other. He just made a bad choice, but it wasn't your fault.