emmab, if it helps any, I went through a divorce (not to an alcoholic) many years ago, and the first year was FULL of moments like this. It gets easier, it gets better, and I'm sorry to tell you, it just takes time. You have healing to do, and you're just getting started. The world continues to move on in the meantime and that can feel disappointing, but I promise that you are going to catch up.
I want to say, though, that I'm sorry your family members left you behind on the 4th of July. You may find that you have to ask explicitly for the kind of support you need -- like a solid plan for holidays. They don't have a rulebook for this stuff either, and sometimes that's going to come across, like this time, as a bit mean-spirited.