Excellent advice, everyone!
Wow, let's just say, "The fediverse isn't typical social media" -- and yes, Jim, there IS intelligent life in the universe.
As for what's getting ripped off: photos, posts, graphics, articles, entire freaking books (wait for Elena's post), audio files, our identities... you name it; it's showing up (usually on sites with not-so-great English).
If you do try and exercise a DMCA, make sure the situation really is infringement, or the courts could rule against you for legal fees and loss of time. For example, this case backfired on Steiner who tried to use the DMCA...
If they're reposting content but making it clear where the content came from, that's not exactly infringement.
You probably have a solid case if they are using content without indicating source at all.
The challenging part in your case is that your content is all over the internet. It's not like one site, but many sites, and there's a growing number of articles about you published by other periodicals, etc, reusing the same images, plots, etc. That starts to get very difficult to keep a handle on and make a case for as 'intellectual property' when the 'story' and content components are spread all over the web. You might find that it's an endless game of herding cats.
If you haven't started already, keep a dossier on all the sites you grant interviews too, etc, and a copy of the written agreements made with them about what they use and how. That might become important in a legal situation that needs to backtrack links on claimed infringed content and where it came from.
Likewise, keep a record on all the sites that you did not give rights to, and bring the hammer down on them before it gets further out of control.