I've talked to some more of my family and friends about this.
What's odd is that everybody who knows me personally has said that the pros outweigh the cons and that they would go and have a good time, reasoning that the event happened a long time ago, I don't care about the girl, and Dave has apologized.
Meanwhile, almost everybody here has suggested I cut him off entirely, not go, and wouldn't have engaged with him at all if this had happened to them, reasoning that I was forced into submission and that event has clearly left a scar that I have not gotten over.
I still haven't decided, but now I'm leaning more towards not going. Part of me thinks that if I go, I'd be forced to overcome this and be comfortable with the past, able to move forward - whether that means attending his wedding or just using the bachelor party for a fun experience where I'm around some friends.
The other part of me thinks that I need to remove any chance of running into her or him to avoid being reminded and brought back to that event. That, along with the fact that I wouldn't have forgiven him if it didn't impact my job, seeing as we were co-workers. All this even though he's apologized, and more recently meant it, because I still happened upon Sara living a happy life with no remorse for doing such a s****y thing.