In "The Immunity Syndrome" it's established that Spock has a telepathic link to other Vulcans, so maybe the same thing is affecting him here.Kind of a nifty idea...escaping destruction by going back through time..but how'd they discover time travel before interstellar spacecraft?
Why does a Vulcan revert to primitiveness simply by going through time?
Heavy use of Hodgkin's Law of parallel planet development too.
The drama is weakened because you know none of this will take, but despite this..I loved this episode as a kid. There's no hate in me for this. I can't say it's really a good episode though.
As far as taking the disks from the Library, yes, there is an unknown factor. They might not work without a reader. They might (though I think it's unlikely) explode. But once they are gone they are gone forever, and as a certain Captain said, "Risk is our business!". Too seek out and learn about alien worlds and cultures. The Sarpeidon library seemed a unique opportunity to further that, totally lost. Maybe the original title, "A Handful of Dust", was more appropriate in that respect since that's what they are left with, in the form of an cloud of superheated space dust and gas.