It’s very important that you recognised and disengaged from the conversation. SO MANY Newcomers to the site just don’t know how to walk away.
I get what you’re saying though… it must feel like you’re letting him get away with lies and excuses by just disengaging?
The reason he starts these arguments and attempts to draw you in - because what you are doing is working. He knows you are detached and won’t engage, so he’s trying to drag you back in with provocative statements like “I bet you wouldn’t xxxx”.
Take heart that he’s trying harder. It means he has noticed you’re becoming stronger.
Perhaps you need to reframe things so that it makes it feel like you’re not letting him get away with blatant lies.
Rather than “I’m not talking about this with you”, perhaps try:
“I’d explain why you’re wrong, but arguing with someone who is intoxicated is a fool’s errand.”
That allows you to make it clear that you don’t agree with what he’s saying, but also allows you to walk away from a conversation disaster waiting to happen. It also places the responsibility on him to sort out his alcoholism.
Also, remember that actions speak louder than words. If he’s saying “you would never do xxx in the bedroom” - buy a vibrator and leave it on your bedside table. Nothing says “Yes I would!” like someone who’s prepared to have a great time without him!
You did really well. Keep it up. There will be a lot more s**t sandwiches to swallow going forward.