(Disclaimer - I am still with AH, and he is not abusive in the sense that you describe)
I like your letter. I'm glad you wrote it for you. If it were me, I would not give it to him and especially considering your second post in which you brought up domestic abuse. He will see blame whether or not you meant it in that way. I guess I just see things a different way (and my situation is not yours). I got tired of discussing the alcohol. And then I stopped. And then I set boundaries and started to detach. When I told him we need to let each other go, I stated that I care about him and am concerned about his health but he's also an adult and should be able to live the life he wants (as long as he isn't drunk driving. Etc and that the kids are ok). I have written letters like that for me.
I think the break would be good for you.