I finally got it unblocked, but only thanks to a former colleague (engineer) who now works at Facebook. If that didn't work, my next step was going to be filing a lawsuit, just to try to get their attention.
A summary from spending a month trying to get this fixed:
1. The "Report" link doesn't actually do anything, or if it does, you have to get loads of people reporting to surface it to a human.
2. The best resolution may be through Ads billing, by trying to post an ad and reporting a problem displaying an ad.
3. This affects a lot more than just blocking links. It also affects messages in private DMs (including from a Facebook for Business inbox), links on Instagram, any Facebook APIs you may be using, and even getting password reset emails to that domain.
For more context, here's my post: https://watilo.com/facebooks-community-standards-censorship-...