Thanks. Your boss being a jerk is logically irrelevant to your alcohol problem. Don't mix the two, it's your employers job to weigh such things.....
My advice is that you go straight to HR and tell them what your therapist and doctor said and that you want and need additional help with your alcohol problem and you want to keep your job. Oh, and then do exactly what they say you should regarding getting help.
I cannot guarantee good results, nor can anyone else. It turned out well for me at a large US company 9ish years ago. I can only assume that it might work just as well now, but again, that is a best case scenario.
Worst case scenario, you know that already.
I wish you well.
It is your choice.
I CHOOSE not to drink today.
FG