Lots of good advice in here. My 2 cents:
1) Don't worry about the future. Unless your city is really, really small, there will be other work for data science people.
2) Don't worry about your record or questions about why you were let go. You can always plead politics. It's a big firm, and people know there's politics in there.
3) Don't focus on the boss. Your new boss doesn't want to hear that you're uncooperative. Just stick to the politics line (boss couldn't get the budget for our group, blah blah).
4) Why on earth would you be blackballed? People do not generally use their networks like this, save for the closest friends. Have you ever looked at LinkedIn? Every post is happy happy. Or anti corporate politics.
5) Definitely start looking for a new job. It won't be strange why you've suddenly got a lot of half days or sickies.
6) Get a lawyer. The angle with the boss violating policy could help you. Also lawyers are generally useful in confrontations.