Expectations
In your original post, you worry that your fiance might become a future alcoholic. You don't have to worry. He already is one.
Also, you talk about certainty. I am here to let you know that there is absolutely zero certainty in life. Whether you marry an alcoholic or not, there is no guarantee. Ever.
please continue to read and study so you can weigh your benefits and risks to make a decision that works for you.