Hi
Concerned123 
to SoberRecovery. Here you will find support and understanding. I hope that you will continue to read and post here.
I think it is great that you have written this letter. I have been in this type of situation with loved ones before, too. They did not know that they were alcoholic or that their life and relationships were negatively affected. I think it is good to communicate this to your partner. Please know, though, that a key mechanism of alcoholism is Denial. When in denial, the alcoholic cannot see the truth, no matter how many times we tell them and no matter how dramatic we are in delivering the message.
Have you heard of AlAnon? AlAnon is a "fellowship of relatives and friends of alcoholics who share their experience, strength, and hope in order to solve their common problems." You can find a meeting here:
How to find a meeting in the US/Canada/Puerto Rico At AlAnon meetings, you learn how to deal with the issues that arise because of alcoholism. AlAnon saved my life. I hope you will give AlAnon a try. (((hugs)))