They must be paying you a hell of a lot more than they're paying 97% of us. Why bother? Just export your content (they provide the means, and it comes in a nice little zip file full of individual html files), then terminate your paying membership, and DELETE your account before 91/2020 if you don't like their terms and they refuse to change them (which they still could, prior to 9/1, right?)

Why would you sue? Open a blog. Write offline and submit to a real publisher. Don't waste time, money, and energy on a lawsuit.