I am making an actual abuse report.

You'd probably have more luck marking them as spam in your client. If you're using a webmail service of any note, you're helping to train the filters used by others, and as a bonus, your own profile means you're less likely to get them in the inbox in the future.

Also, if you're in the USA, you should report those messages to the FTC.

If you try to unsubscribe from an email list and your request is not honored, file a complaint with the FTC. via https://www.consumer.ftc.gov/articles/0038-spam

You appear to have missed the part about this being my own mail server.

And I don't need any more luck; my initial problem is solved (I no longer see spam from Facebook, and I am taking steps to ensure they are aware of their problem, in case they weren't).

The problem was worth the time I spent on the config; it is manifestly a waste for me to involve the FTC, since I don't have to worry about Facebook's spam anymore and am willing to eat the tiny amount of bandwidth involved.

I am pretty sure a Facebook dev has already set up a rule on the abuse inbox to delete any emails coming from your domain.

Thereby resulting in facebook being a worse software for the average user due to their abuse of this one user. Win win for someone who doesn't like facebook.