This is great stuff Bronxblue. I am not an IP attorney and unfortunately can't give you good technical legal advice about the black-letter law involved. However, I can help you locate a good lawyer to work with in MI (if Bronxblue is unable to take it on pro bono - hint, hint). I have a few contacts at big firms there who are so-called "Michigan Men" that might be interested in helping issue formal demand letters, etc. Shoot me an email if you're interested.
The best advice I can give is that, once you start weeding into the world of figuring out how to fight back, if you encounter a lawyer on the other side make sure you have a lawyer as well. Don't try to deal directly with lawyers because they will (1) poo-poo you, and (2) act high-and-mighty and work hard NOT to help resolve things. Lawyers love preying on non-lawyers in these kinds of disputes. Heck, I'll make a phone call for you if you encounter an a--hole attorney. Just let me know - I love f-ing with other lawyers, if only because most of them are tools.