Here is a little update on my own situation. I also have some new information from others.
It has now been several months since I mailed my letter to Sanders. I have not heard anything by mail, email, or phone. Even though I check here to keep up with others' cases every day, I've nearly forgotten my own. I'm hoping it stays this way. At some point I plant to make a version of the letter I sent available for others since it seems to have helped my situation.
I've been in touch with another letter recipient who somehow missed all attempts Sanders made to serve her. She received a default judgement which she is now appealing. Sanders attempted to push the new hearing date out into the future. She opted to keep the original time. It seems, as others have speculated, that a large part of their strategy is to make you sweat it out as long as possible. Sanders probably thinks people will settle if they can make them worry long enough. I don't spend enough time in the legal world to know if this is common practice, but it seems to me that they know they have a weak case.