This talk of the history of the Espionage Act feels like a lot of hand waving. You make it sound like the government cherrypicked and misapplied some old law in order to stymie Snowden's defense. I don't believe there ever was (nor ever will be) a scenario where leaking national security documents to the press is protected as whistleblowing. This is not specific to the Espionage Act, I don't think "yes I did it, but it was for the greater good of society" is typically a valid defense argument in any criminal case.
(And it's offtopic but I disagree with your characterization of the Lavabit case. Lavabit wasn't on trial; they were served with a valid wiretap order that was signed by a regular non-secret non-FISA court judge and based on reasonable evidence. That's how it's supposed to work. I wish all national security cases were pursued that way.)