I am sort of the anti-christ of co-dependency. Then my daughter got addicted to heroin and I developed a full blown case of co-dependency.
When I look back, upon that time, in my life, my own co-dependency was rooted in a belief that I had the ability to control my daughter and cure her addiction. And Lord knows, I tried. I could not figure out why....why she was doing this to me. You see, I managed to make her life and addiction all about me. That's what we co-dependents do. And we are sneaky little devils,too. We do it all in the name of our love for them cause we know what best for them...and forget about the concept of free will.
Your friend's addiction, the life style, the moods, the abuse are not personal. He hates himself and projects it all on you. Only way it can impact you is if this abuse validates your own feeling about yourself. Sounds like you are in touch with this concept.
Since you have determined that a support group and therapy does not work for you, what are you going to do to heal yourself? There is no magic formula that's going to make it all better. Have you considered getting out of the house and doing good, somewhere. Volunteer your time. Meet new people,.. Become exposed to some new ideas. Learn something. Find something ( not someone) to be passionate about. Don't like people? How about animals. Shelters are always looking for new lovers. Imagine the possibilities.