The dude planned this for years, he said it himself. He had plenty of time to simply take evidence of what he was going to blow the whistle on. I don't understand your argument.
> impossible to expose the information in any other way
Except for the many oversight channels that exists which there has yet to be any evidence he used.
> For example, there may have been evidence of other crimes, and there would be no way he could sift through the documents while still working.
If I understand your argument correctly, it's: "it's possible something here is illegal so let's just take all of it." I shouldn't have to explain why that doesn't jive.
> Also, he recognized that he needed to leak slowly in order to keep the story afloat, or else he would get buried under propaganda and forgotten, as has happened to other whistleblowers that released all at once.
None of this addresses the fact that it seems he did a recursive pull of supersecretnsadomain.gov and deuced out to China under the pretenses of whistleblowing.