I would have tried to negotiate for a larger settlement, two weeks to sign an NDA is actually pretty reasonable to me. Assuming you didn't burn any bridges on your way out of your last company, you should be able to just go back.
I've done it, I don't think him telling the entire world is going to accomplish much. Maybe you'll get a couple of retweets, but that can also scare off future employers.
Generally, you should take your emotions out of the equation, and evaluate what's going to benefit you the most. Is mouthing off on Twitter really worth $6,000 or $10,000?