On: ...was granted a divorce because he was constantly working calculus problems

[quasse]

I think the author is providing you some background information about why the files exist, and then saying that the story about the drums and calculus is probably true.

I don't see any claim in there that the wife was a lying tool of the FBI. These files would have been compiled after the divorce anyway.

[EpicEng → quasse]

The author certainly implies that those charges are false.