I run a small photography business. A few years ago Facebook deleted a few fb events we had created with a few hundred attendees each. They never gave any reason for the deletion or any warning. Like you, we hit our heads against the support-brick-wall for a while. I estimated damages around £10k and filed a small claim against them.

I used the EU small claims procedure which allowed me to sue FB Ireland from the UK, where I live. You must sue FB Ireland, I tried suing fb uk first and that was a lengthy and stressful mistake. I'm not sure what you will be able to do from the US if that is where you are based.

Long story short they settled the matter out of court. I never got an explanation as to why the events were deleted.

File a small claim, anyone can do it, it'll get their attention and they will probably pay you damages rather than argue the what and the why of your case.