I’m so sorry about everything that happened to you. Have you looked into filing an EEOC complaint? No matter what your severance agreement says, you cannot legally sign away your right to file such a complaint. Even though your lawsuit didn’t go anywhere, the EEOC might be able to help you get justice. I don’t think you need to pay for a lawyer in the first stages of that process, though it might not be a bad idea to consult one.
Also, you mentioned that working the late shift made you sick, and that you had been ill prior to going full time at Squarespace. Did you ever request ADA accommodation from Squarespace for any reason? That’s another possible avenue for seeking redress. I’m not sure they can do much for you if you didn’t bring it up at the time, but it may be worth exploring.
You are better than the terrible things that happened to you and you will get through this. Thank you for speaking out on behalf of yourself and others. Take care of yourself!
(I am not a lawyer or an HR expert or anything; this advice is based on my own experiences and research.)