Oh wow. That sucks on so many levels.
It's a sad fact of reality that copyright law makes it easier (and even more sensible for the big guys) to accuse people of infringement with the slightest, flimsiest excuse than it is to defend against it.
I worry about this for myself (as any superhero fiction writer should) because the superhero giants, marvel and DC, are quite litigious. As I understand it, they even have the word superhero trademarked between them.
I'm afraid I don't know anyone who I could point your way. I wish you luck.