In the tv appearances I’ve seen Page in he comes across as stupid. However another interpretation is evasive. I don’t think he’s stupid. He graduated from the Naval Academy at Annapolis. He has masters degrees from Georgetown and NYU. He also has a PhD from the university of London. He speaks Russian. He’s not stupid.
The biggest problem with the theory that it’s Page I think is that he’s too easy to guess in order to be considered a secret source. And it’s difficult to see how his outting could expose intelligence assets since the Russians have already surely put him on their radar. But then the FBI has a history of using fake national security arguments to avoid disclosing information so maybe that is what it’s about.