I have a similar situation with my son. Love the boy hate the addiction and it seems the only way they will stop is if they want to. No amount of persuading coaxing crying will change. You have to have boundaries and if those are crossed you or your partner has to leave the relationship
Don’t give boundaries that you aren’t prepared to enforce if they are crossed but I’ve reached the very painful point of telling my son to leave as I have a life and i can’t live it like this
Good luck I wish I could say all ends well
Who knows