I left in secret 3 years ago. My ex was abusive, but not alcoholic (although that may have changed now, not my problem).
You may need more time than you think. I had a couple of helpers and a van, and still took all day to move stuff out while he was at work. And I had to leave all my books behind, I simply ran out of time.
My anxiety on the day was through the roof, but I managed to keep everything calm for the DC. My oldest was 17 at the time, and a real help. She can keep secrets and wanted out, too.
I reckon your 17 year old will be a great help. I recall something in your previous thread about him not getting on great with your H? He'll keep things quiet, then.
I left a letter, for all the good it did. He denied each and every point. He told everyone he didn't know why I left (they were pretty much all on my side, he hasn't made any friends with his behaviour) so my dad asked me to send one letter detailing exactly why, to shut him up. Didn't work, he denied everything again.
And now I have a better life, he doesn't know where we live, and we are in the same town, and the DC and I are flourishing. I may even begin dating soon.
Despite the crap around the time of leaving, it was all worth it. You can do this and it will be worth it for you, too. 