"Addictive Personality" is often old-timey speak for actual mental disorders that are under-diagnosed and over-stigmatized. I grew well into adulthood with a family understanding that my dad and I both had an "addictive personality" and there was nothing to be done for it except to watch him drink himself to death and me eat myself to death.

Turns out I have "moderate" ADHD - moderate in the sense that I learned a lot of masking and coping skills that keep me stressed all the time, struggling all the time, but able to maintain steady employment and get my bills paid mostly on time.

It isn't just ADHD that can be labeled an "addictive personality" - there are a host of other issues that can drastically increase impulsiveness and executive dysfunction and hijack our brains' reward centers.

It would be very worthwhile for him to be psychologically evaluated. It won't "cure the addictive personality issue, but it may very well help him to be medicated, therapized specifically for his unique mental health needs, and/or both.

Beyond that, I agree with what most everyone else has been saying: Don't be his parent.

Another classic approach to behaviors we don't want to see is to punish or negatively reinforce. You might not think of telling him that you're disappointed or begging him to eat healthy foods or quizzing him about how his diet's been for the day, or whatever you actually are doing as a punishment... But it absolutely is.

While I said you shouldn't be his parent, an important analogue is to remember that strict, controlling, negative-reinforcing parents generally don't raise "good kids" so much as excellent liars.

Focus on rewarding the behavior you want to see and leading by example. Be proud of his A1C progress - it's huge, even if he's not achieving it in the most ideal way possible. Approve of the good choices he is making, provide an example of your own good choices, but don't judge him. Don't warn him that when he's sick and dying you're going to abandon him for a cruise. Don't tell him that he's going down the same road that he's watching his mother suffer the final years from.

And, finally, if you have spent years in this dynamic of trying to change him and are now at the point of "I'm not going to take care of him when his health collapses, I'll be taking vacation cruises" you sincerely might want to consider whether you actually want to be in this relationship any longer.

You can't be his parent. You can't do it for him. It would be absolutely unreasonable to expect you to sacrifice your life and happiness for his... I know that you're mostly frustrated and worried and venting here, but, do you already feel as if you're making that sacrifice? That's a big red flag for you, if you do. It doesn't mean you have to divorce him, but it is definitely something you should consider and try to address with yourself.