Mizzuno, I'm really glad you posted this. You are getting some amazing words of wisdom and support here.
Just two little thoughts to add from me.
First, you might consider what specifically would count as a successful experience at this wedding for you? I bring this up because it sounds like keeping expectations realistic at this event will be important.
Second, remembering back to my wedding day… it was crazy. The people. The logistics. The expectations. The food…. It would not have been the ideal day for me to work through any additional or outstanding emotional issues. I just would not have had the bandwidth. Again, this goes to handling your expectations so as not to be disappointed.
Wishing you the best on this difficult challenge!