He is an adult, yes?
I understand he has an addiction, but he's not being held anywhere against his will without access to the many resources available to help him fight this.
He simply does not need YOU specifically to do anything for him. If he were truly motivated to get help, there is no obstacle that would be able to prevent him from getting it. At the very least, NA and AA meetings are free.
To me, it rings of manipulation. Good for you for staying inside your own hula hoop.