The "additional examples" left unspoken could be attributed to other killers, unless they too were in the same direct line between Argelius and Earth.
Well, of course the computer was only listing similar instances with unidentified killers, but the pattern was enough to allow Kirk and Spock to deduce the existence and nature of the Redjac entity. The obvious implication of the script was that the additional examples would also have been the entity's work. There would have been no reason to include it in the script if that hadn't been the writers' intent.
Even James Blish refers to Spock as a Vulcanite in his first two episode anthologies or so. Could've been residual phrasing from the show's bible, perhaps.
No, that was surely Blish's own coinage. In the early volumes, he took considerable liberties and added his own ideas to the stories; indeed, he even wrote them as if they took place in the same universe as his
Cities in Flight series. It was only in later volumes that he confined himself to straight adaptations of the scripts.
The first-season series bible only says that Spock's mother is human and his father is a native of the planet Vulcan, without offering a demonym. The first season referred to people from Vulcan as
"Vulcan" nearly twice as often as it used "Vulcanian," with "This Side of Paradise" and "Errand of Mercy" using both interchangeably. It was standardized as "Vulcan" from season 2 onward.
Blish was also the first writer to make it clear that ST's Vulcan was an extrasolar planet, not the conjectural planet Vulcan that was once believed to be closer to the Sun than Mercury was. People today have largely forgotten about that Vulcan, but at the time of TOS, it was still well enough remembered (at least among the science fiction audience) that Blish presumably felt the clarification was needed. (Given that Spock was originally suggested to be "probably half-Martian," I strongly suspect that Roddenberry initially intended Spock to be from the cis-Mercurian Vulcan, but his science advisors convinced him to make it an exoplanet instead. "Amok Time" was the first episode to make it reasonably clear that Vulcan is not in the same system as Earth.)