So. I'm sorry. My work has been stolen by Chinese and other shops (including several in the West).
That said, it was kind of an error to not trust your original instinct that it was a fishy order. They will only stop selling now when it stops making them profit. They will use scripts to make new websites and shops. Theft is their whole business model--and they've gotten good at it. Using your time to wack a mole their listings will waste your time and not achieve your goal of stopping them, unfortunately.
Your only option that leaves you in the end in a better position, really, is to make new items/products and accept that those 3 years worth of products will be undermined from a sales point of view. I know that's rough to hear, and may be depressing (def, talk to a counselor btw, this is definitely traumatic).
On a semi-positive note: your products being stolen is a mark that you're making quality stuff. This has happened for centuries to quality inventors and designers ♥️... And don't think of it as 3 years wasted, think of all the better designs you'll create now with all that practice! The Beatles became legends because of all the practice and trial by fire.
Oh, and also, if possible: add watermarks/witnessmarks to the photos and even into the files. Though, even that won't stop a thief who's dedicated. Fortunately, I suppose, as you up the difficulty to steal your future products, you'll make it less likely to reoccur and hopefully the IP playing field will improve over time.