Depending on what you signed at the police station it may be a closed case already. Did you sign a confession? I would say only talk to a lawyer to see if he can get some kind of deal that is lower than what you were charged with. Other than that I think you are pretty much done.
If the other spouse entered the agreement with the intent to claim nothing from the wealthier spouse, regardless of the exact amount of assets or income, then this would be irrelevant to the other spouse's consent to the agreement.
However, if circumstances made it clear that the other spouse would not have entered the agreement, as it was drafted, had that spouse known of the full extent of the wealthier spouse's assets and income, then clearly the agreement would be void as lacking the informed intent.
The problem is the proof of such an invisible, elusive state of mind. How can we say what would have been the intent of the other spouse if full asset and income were disclosed?
All proof would have to be circumstantial and very sketchy.
On the other hand, we have the written agreement in front of us, and can easily read it word for word to see exactly what the parties intended and agreed. If there's no stipulation as to an upward limit of assets or income, then full disclosure could be seen as irrelevant.
In real life, if no one objects to the agreement after assets and income become known in full, then there would be no need for a purely intellectual debate, so on with the marriage.