I’m not sure if I’d say that he “puts his faith in socialism” since he was around for plenty of the USSR and was a dissident and antistalinist! Then again, Khrushchev claimed to be a Marxist despite being a fucking collaborationist in terms of professed beliefs, so maybe that’s just the failure of Soviet education in Marxism.

I can believe, if the letter was real, that Stalin would keep it for his entire life due to the guilt, but it doesn’t seem to be or else it would a) have been reported on sooner and b) be in the damn archive! Of course, the two historians give it the cartoon villain characterization you describe except for the Lenin one, which they admit was for a more human reason. I don’t see why he’d even bother with the Tito one except that it (if it was real) would be an excellent show of rhetoric. I think only the Lenin one was real of the three though.

And there are conflicting stories, but in the one that mentions there being five letters, the other two were forgotten by Khrushchev, who was telling this to a third party who told this to the historians, so you remembered all of the ones that were attested.