That was dick of him to leave you at the party , but at the same time, you should be past being upset about being left at the club.

You should have addressed the situation sooner than this. Even if a wedding was coming up, a simple "Hey, what happened?" could have sufficed. At least then you would known your individual standing with him.

Now you're at the point where you simply don't want anything to do with him, but you're feeling obligated because what's going on with his mom.

If you truly don't want anything to do with him while his mom is dying because of what happened at the club, then you just need to never have anything to do with him again, ever