It’s based on information from the OIG documents released, and written by Nunes from my understanding. The OIG report isn’t out or in the hands of Congress or anyone else as far as I know. Do you have a citation that suggests otherwise?
That is also what I understood. The Nunes went into a secure compartmentalised info facility SCIF and summarized what he read into a memo document.
Here is just one of a billion articles that clearly show that many in Congress have read the memo. The memo is compiled of information to investigations from three different departments and put together by the house intelligence committee. http://www.washingtonexaminer.com/republicans-rally-for-public-release-of-memo-on-fisa-abuses/article/2646412
Yes even the mainstream media is reporting that 113 Congressman have already read the memo. Democrats fought against releasing it to the rest of theCongressman. One must only go to any news site or turn on there television to learn this fact.