I don't have a source. I just know that some people have apparently gotten revived after that much time. Now, did they follow the protocol? Did they have >95% pure SN? Idk. Not sure how common it is either, depends on multiple factors I'd imagine.
That doesn't make sense. If they die at 45 minutes, the brain is permanently dead after 6 minutes, there is no possibility of revival after 6 hours. You might be thinking of the previous PPH recommendation to find solitude for that period of time, and now it's recommended to be 24 hours. I don't think that's due to possibility of revival, just to ensure nothing goes amiss.
"The intake of an excessive but non-lethal quantity of sodium nitrite guarantees a longer survival interval, with the possibility of accessing an emergency department and receiving the appropriate therapy"
The only exception is if the protocol is not followed appropriately. In which case, maybe the individual had a full stomach and that interfered with absorption. Or they didn't take the full amount, etc, etc.