I was in a similar position with a boss who wanted me out and who did everything she could to make me quit/fire me. It really is a crappy thing. The good news is that you are out with severance!!

I agree with kaliope about moving on. I would not go back to a company that treated you that way unless they drastically clean house. I'd ask your senior connection for some job leads or introductions at different companies. It might help you skip some of the job hunt steps that are the most nerve wracking!