I'm just another garden variety alcoholic weighing in.
I do vaguely recall my former fiance and current girlfriend suggesting that I cut back, significantly. She may have even suggested I look into going to an AA meeting. I recall feeling offended, especially because, at that time, my life was still very much in order, or so I felt. I'd felt that if anything, the problems in my life, to include a somewhat tattered status of our relationship, and serious depression where my reasons for drinking. I felt almost as if she was calling me weak and a bad partner.
She didn't want me to quit, per se, but just cut back. She also enjoys a drink, glass of wine, or pint of beer, and it seamed that alcohol was such a focal point of our lives, I felt that giving up drinking or cutting back meant a poorer quality of life.
Fast forward 3 or so months, and my drinking had rapidly escalated to the point of daily withdrawals, severe anxiety, and secretly drinking much more than she'd realized. After a particularly pathetic weekend binge, I called in sick on a Monday and ended up visiting my doctor and coming clean about my alcoholism. My NA fiance was absolutely shocked when I called her from the doctor's office with the prospect of going into rehab.
Long story short, I didn't go to rehab, struggled to stay sober in early sobriety, but then started working a good AA program and pieced together 7 months of sobriety before a thankfully short and minor relapse. I'm thankful for the relapse because it's been instructive regarding my continued recovery.
Here's my point: there wasn't a conversation she and I could have had that would've compelled me to seek recovery. I had to get that desperation on my own. If I had stopped for her, I'd have just been resentful. I was a fearful person during my drinking (I still am, but I'm getting better), but I wasn't afraid of the consequences of my drinking (i.e. death, DUIs, damaged relationships, work termination). About every addict/alcoholic I know, and I now know MANY, feel exactly the same.
What she should have done is identified boundaries, and stuck to them. She thought of her behaviors as being kind and loving, but most of her behaviors were just enabling my alcoholism.
Stop enabling your AH, stop defending his behaviors to yourself and anyone, and terminate your involvement in any and all things that relate to his drinking. Addicts cannot sustain active addiction without enablers. If he's like most of us, his progression towards a bottom that's sufficient to motivate recovery/treatment will rapidly accelerate. If he's ever to recover or survive his disease, then he has to walk that road alone.
Just so I'm not all doom and gloom, I'm in recovery and my girlfriend and hopefully one day fiance and then wife goes to Al-Anon (because she sees it working in her life). I work as good of an AA program as I can and my recovery ALWAYS takes priority in my life. We no longer live together, but that gives us a chance to focus on our individual recoveries. I think she would agree with me that at no point in the approx. 5 years we've been together have we been more optimistic about our individual futures and our future as a HEALTHY couple.
Best of luck.