Thank you for this. I share much of your experience, both personally and with other family members, and my former partner is a person addicted to substances. Although I do see him as ill, I agree that there is a tremendous difference between his illness and an illness such as cancer. And I have to say that about my own (other) illness: I chose to do all that I did in the past when it came to my codependency. No one forced me, although the IMPULSE came from places within me that made me feel as if I HAD to do some of the things I did. But only with a lot of critical work on myself was I able to begin to unravel the rat's nest of "causes", and to do THAT was a choice, as well.
Choice is the difference, and it relates to both sides of the street. Both a person addicted to substances and a person who we call "co-dependent" chooses to engage in self-destructive behavior. This makes neither one "good" nor "bad" -- it's simply illness –– but only by taking responsibility for one's actions can recovery begin.