That wouldn't work as a defense for Manning. You can't just unilaterally decide something should be declassified based on those protocols. You would still have to go through proper channels to declas.
I know, it's a tricky situation. How do you operate legally in a system that is corrupt? But in this situation, I think whistleblower protections are what's relevant, and not the law on declassification. It would set a dangerous precedent if a court decided that any joe-blow could declassify something on their own.
It does. That's why there are laws for whistleblowers.