When I talk to some people in RL they don't react the way people on here do. I came into work a while back and told a colleague that my husband had told me to fuck off in front of our dd and had said I'm pushing his buttons so it's my fault. She just looked a bit non plussed and said 'urgh men' and that was it.
She probably felt extremely awkward and didn't know what to say or whether you just wanted to vent or wanted serious help. It can be very hard to judge this in a workplace context. Whereas here, we know you want help, we have time to formulate our responses, and we don't have to navigate working with you on top of all of that. A lot of people in RL just won't be equipped to give you helpful input here, sadly, as you're finding from your own family, and others will have been burned in the past by trying to help people who didn't want to be helped.
Reposting from prev attempt to start new thread - red, I know it might feel like we are again coming down like a ton of bricks on something you thought was not only normal but 'lovely'. It must be easy for you to feel like we just don't understand, like our expectations of you are unreasonable. Maybe they are. But we have to have them, because your perceptions of 'normal' have been warped beyond recognition to a family not steeped in substance abuse. The first time I took my child to a party like the one you described would be the last, and I would have walked out by the time a second person sparked a joint.
If your daughter was able, physically, mentally, and emotionally, she would be screaming at you: 'Fuck him! What about ME? What about my precious life? You're the only one who can help me, and you aren't!' It's down to you. It must feel very hard to step up. But you can. You can dig deep.
What is the thing you'd need to see which would stop you putting into action your plan to leave at Christmas? Because I think anything less than 'H is in treatment and admits he needs to stop altogether' is gong to be too little.