I think there's a lot more going on here than I can figure in a single post. If you don't want to go though, I think you should at least cancel, not just not show up.

That said, I know even when I've only had a couple of drinks, I have a shift in cognitive abilities (people often think they don't which is how we end up with people driving under the influence). So, I think going if for no other reason than getting clarification would be worthwhile.