Looking back over my 20+ year relationship with an alcoholic, I'm pretty sure I would not change anything about him, even if I had the power to. Our marriage was what you describe as perfect for probably the first five years. It was not too bad the first ten years. In the last 5-10 years, it became incredibly painful. I'm not convinced that this is entirely attributable to his progression. I'm fairly certain it had as much to do with my changing as it had to to with his.
If I could change anything about it all, it would be my awareness. I was slow to become aware of me, my issues, my dynamic in all of this. I slowly lost myself and became someone I didn't like very much. I don't think that it is his fault. I knew what I was dealing with, but I figured I could change it to suit me. That was my biggest miscalculation. I wish I would have realized sooner that my path was diverging from his and there was really nothing I could do to get him back in line with me.
Granted, my situation is different from yours in that I met him when I was 24 and I 'grew out of him.' I just wish I would have honored my inner self and listened to what my soul was telling me before things got so bad.
I don't know if that helps in any way, but maybe someone will get something out of it.
L