I am inspired by your attitude facing what must be incredibly difficult. As far as specific support group information goes, I don't have any. However, you should be able to find a Nar-Anon, ACOA (Adult Children of Alcoholics) or other such support group in your area. These are twelve step programs helping those affected by loved ones that are addicts or alcoholics. I have experience from both sides of this situation, so I'm hoping a little insight helps.
My father had a long career of substance abuse and sex addiction, abandoning us as children to pursue it. He is now 74 years old and an evangelical minister of music for 30 years, traveling the southern U.S. to tell his story of how his faith helped him overcome the disease of addiction. I have spent a lot of time in therapy dealing with the abandonment and eventual addiction of my own. From that perspective, the greatest wisdom comes from the realization that there is really very little you can do for your father – he must make all the steps toward recovery himself. You can offer love and support to him, which can make an impact, as it is a difficult journey. Being in this position is difficult for you, too, which is why such programs as Nar-Anon and ACOA exist. Similar to what they tell you on the plane about putting on an oxygen mask, help yourself first, then your father. If you’re not prepared for the mental and emotional challenges, you may hurt more than help him.
Regretfully, I am not a parent, but perhaps close to your father’s age, and have been living with HIV/AIDS for 10 years. Probably like your father, my early years after being diagnosed were spent trying to escape my middle age and diagnosis through crystal meth abuse and the sex addiction that came with it, which exacerbated my health issues and almost cost me my life. I have survived cancer, chronic hepatitis B and a bleeding disorder for four years now. I am living a clean life, practicing yoga almost every day, and pursuing dreams I had forsaken when I received my diagnosis. My health is miraculously good, when you consider what I put my body through. During the worst of my addiction, I was a bag of bones, staying up for more than a week at a time.
All of this should encourage you that there is hope for you and your father. Arming yourself with the strength from the support groups for you, then loving and supporting him is the well from which great miracles can spring.
Peace, light and hope to your family.