Oh dear God are you still here?
NO. THERE IS NOTHING IN WHAT YOU HAVE POSTED THAT AUTOMATICALLY NULLIFIES OR VOIDS THE SEVERANCE AGREEMENT.
The devil is in the details. If you take the entire agreement to an attorney in your state, there is about a one is sixteen million chance that he might find some language that voids the agreement. You can then pay back all the severance, apply for unemployment and file a lawsuit.
Of course, the fact that this happened over a year ago means that unemployment will be denied since you're now beyond the limit to file for that time, and your lawsuit will fail because EVEN IF THE SEVERANCE AGREEMENT IS VOID YOU STILL DO NOT HAVE THE BASIS FOR A LAWSUIT unless you have some kind of supportable and verifiable proof that you were selected for this treatment BECAUSE of your age and/or gender, and can find a way around the fact that the SOL has passed for a discrimination claim; or, alternately, if you have proof sufficient to stand up in a court of law that your boss knew at the time that the layoff was not going to happen.
I am an over 60 female myself, and one who used to teach employers and employees alike how to recognize illegal discrimination. Unless you have left out material facts, that's not what's happening here.