I could see him being told the odd one or two (though even then, its him we are talking about so I have my doubts) - but not so many that he could keep a list and for enough of them to be bumped off to make a noticeable difference.
I don't think he would likely be able to remember their names long enough to write them down afterward.
What was taken, if accessed by foreign spies, might have contained enough information for them to identify potential leaks, run counterintelligence operations and silence our assets. Without knowing what is actually in the boxes, I can't give you an evaluation on whether or not Trump likely was the source of the leaks, might have been the source of some of the leaks, or almost certainly wasn't the source of any of them. What is clear is that he didn't care enough about the lives he was taking into his own hands to take steps. It's willful failure to ensure that the documents were kept in a way such that he could not possibly be putting anyone at risk. It's different from the whole Plame mess (unless it can be proven that Trump is in fact a Russian agent), in that this represents negligence rather than willful misconduct in the pursuit of a political agenda.
IMO it's enough to justify barring him from ever holding office again, at a minimum. How is the CIA supposed to recruit sources of intelligence if the person they report to doesn't care if they live or die? Whether he ends up in jail or not is a question for prosecutors and a jury, but any rational Congress would act.
