Thank you for your question.
WHile you figure out how to handle this you should be filing for unemployment, which opens a new front in the situation but this could drag out for a long time so if you have not done so yet, please consider filing for unemployment which you do on line through links at http://www.ides.illinois.gov/Pages/Unemployment%20Insurance.aspx
This looks like a dance i have seen before where one side makes an offer that is the lowest number it can offer and still keep a straight face, and then your side would make a counter offer for maybe $250,000 or whatever number your attorney can say without giggling.
I don't have the facts but it sounds like the employer has violated multiple civil rights and labor laws and you probably have remedies that would let you win attorney fees. And I don't know if their offer says you get your job back or not. If not, it is a really bad offer and I would hold out for something closer to what the law says you can recover.
You can get a free consultation from some of the labor lawyers listed by location here. You are lucky to be in a union. It sounds like the union is going to bat for you but I only have a bare outline of the situation, and there have been cases where a union sort of sold out a member and then the membaer had to sue the union for breach of the duty of fair representation, and we don't want that to happen, so I think you should speak with a local labor lawyer who can see the documents and get the facts in confidence, and then advise you of your legal rights and remedies and advise of of the realistic settlement value of the claims.
Please follow up on this with a local attorney.
I hope this information is helpful.