Does revealing that the FBI raided Mar-a-Lago for top-secret nuclear weapons documents give would-be defendant Trump some legitimate cause for grievance that would help his case?

There’s also the point that it’s the information that is classified, not the particular physical document. That means that if Trump did declassify the documents, they are declassified for anyone in the federal government who has access to them. They could publish them without being in breach of the classification laws.