Chic, him "not getting help" is NOT an option for you here....You have come way too far to let go of this and let him continue to live off of you while you clothe, feed and provide a home for him with all the hotel amenities.
He may be going to treatment kicking and screaming, but you will insist that he goes to get some help or he'll pitch a tent on the front lawn. do NOT let him bully you to make you upset and back down, believe me he doesn't feel bad when he does it, in his little pointy head, his behavior is justified.
I will send Sammy to keep everyone in check. (he loves cats)