Advice for writing THE letter to my Q

Hello, I have finally gathered the courage to write a letter to my Q (I'm choosing a letter instead of an actual conversation to ensure what I say isn't skewed).

I do not want to remain in our marriage if his drinking continues. So this is where I need advice... For those of you who have done this, how long do you give your Q to get help? Do you set up a timeframe? How harsh are you? I almost feel like I need to be direct, harsh, and hold boundaries.

I've told him in the past that I didn't like him when he drank. He knows it's an issue. But I really think he will get defensive and I'm not sure how to handle it. I already think he will tell me that it's not that bad or that a few drinks after work are ok. I'm trying to come up with my responses prior. Did you do that or did you lay it out in the letter?

I'm worried he won't take my letter seriously.

When is the best time to deliver the letter? I know I can't have a conversation with him once he's opened up his first beer. But it's like... Do I give him the letter and then leave the house? I don't know how to give him the letter or what to do afterwards.

I guess need guidance on how to go about this.

Thank you in advance.