Correspond with copyright thief

I have an alternative health website that sells an ebook (and provides 3 bonus ebooks). Copyright is registered for both the website and ebooks. I was alerted to another website that has stolen some of my copyrighted materials and incorporated them in their website and their own ebook. From my complaint, 2Checkout, their payment portal, has ceased processing their orders as of several days ago. I think they've also locked up any monies due to the website owner. The owner of the violating website has been in email correspondence with me. His tone is badgering and threatening me to assist him to clean up his material to my satisfaction, so he can begin trading again. I am annoyed because his ebook has straightout copied one of my bonus ebooks, and the framework for the rest is exactly my table of contents of my main ebook. I don't want to help him at all and I want him to go away. He is threatening to go to my payment portal, [login to view URL], to make trouble for me. I want you to correspond with this unpleasant man in suitable legalese and in sufficient streangth to stop his causing me and my business potential trouble and to advise me of any protective action I need to take. You will need to review the details of the copyright infringement and correspondence - I will furnish these. In the ideal world, he should be compensating me for the money he has made from the stolen materials.