At this point he is like a bird that has his wings clipped. You are the one clipping them.
You have trained him to be dependent. Reading between the lines of your post it appears that you know it is time to stop your behavior.
I have worked with learning disabled students who become capable, independent workers.
Uneducated Immigrants come here all the time with no English skills and get jobs, because they have a work ethic.
You have to believe it is possible and act that way too.
Of course the real handicapping condition at this point is addiction. The only help you should be offering is to find a treatment center for him. If he refuses let natural consequences take their course. Don't meet his obligations in any way or spare him from the very consequences that might lead him to seek a different way to live.
At this time you can change what you can, yourself. If you change you will focus on your part in this relationship.
IN my area there are al-anon groups for parents Working the program of alanon made a huge difference for me. My son is currently in long-term treatment. But I did the work, made changes, sought recovery, went to therapy and got on a spiritual path long before my son did.
You can too if you are willing.
The definition of insanity is doing the same things over and over and expecting different results. It seems you are willing to learn from those who have some of the same experiences you have.