I dont think writing anything down for them to grasp is worth the energy until they have admitted to their drunken mess. Write it for yourself if you are dating or married to an active alcoholic. I have in 4 years never seen a single thing I have written stick, because he is a blithering drunk still and refuses to admit it ...
Once they admit their disaster then all of the sudden they are " open " and " willing " to even read and "comprehend" the contents of those letters. And even then, they are doing it with an alcohol SOAKED brain which as we all know, is never consistent, remembers Sh*t, and reasonable until at least a year of healing and AA has gone by. These are the facts, and expecting anything more is too much for them. It is almost like being mentally handicapt at that point when you expect them to emotionally grasp anything other than their self absorbed behavior and world. Just keep your expectations in line with the facts of alcoholism. It is true, words are nothing to them. most of the time.