This was under the Division of Property FAQS on the home page:
“If my spouse and I have divided our property, can I file an equitable distribution claim?
In addition to bar by absolute divorce obtained without preservation of an ED claim, the other common bar to ED is prior execution of a valid, comprehensive property settlement dividing the parties’ property or otherwise releasing the right to ED. So long as the agreement is duly executed in accordance with the formal statutory requirements, the agreement might bar a subsequent ED pursuant to the rules discussed below. Such a bar may arise not only from property settlements entered into at the time of separation but also from written premarital and postnuptial agreements.”
My husband’s ex tried to have their separation agreement tossed stating that she did not understand what she was signing, due to being on medication for depression, which we had proof she wasn’t taking when time for the papers to be signed. She also stated that he read the papers to her so he made it sound the way he wanted her to hear it. She had the papers for 3 days before signing them and the only thing he read to her was the original draft, not what she signed. She actually called him after getting a copy of the first draft sighting an error in some of the property and he had them re-done to include that property in the final draft which is what she signed. She did not try this until after she found out we were dating two months later. Her own lawyer told her she would not get the separation agreement overturned and that he would not represent her if she chose to pursue the matter given the evidence that she lied to him about it.
I am not, by any means saying that you are doing something similar, I’m just making the point that a separation agreement is a binding legal contract and should not have been signed if there was no agreement. You may be able to get it modified if there was no disclosure, but all the assets and debts in reality should have been in the agreement to start with including his 401K and pension. If it was mentioned in the agreement then he disclosed it.