When was that published? I mean it's not like he touched the divine and immediately went to to the writing desk. It may have been written well after Dagoth's re-awakening. And considering that the Sermons make it clear that only the Nerevarine can defeat "The Ur" why would the Triunes try to take Red Mountain in 2E 882? Then again if the sermons were written after this giant fail......well, pretty easy to predict the Sharmat reawakening (seeing as he's already awake), and that only the subject of a prophesy made hundreds of years beforehand, by a patron Daedra Prince no less, can get the job done. Not saying you're wrong, but when the the 36 came out would go a long way in knowing if Vivec was well adept at predicting the future or just making well educated guesses based on events that happened beforehand.

As to the library question, and to keep things on topic, that would depend on what you mean by better. Mora's for shear volume, but Jyggs' would be way more organized. Hmmmmm? I'm going with Jyggs on this one. I mean what's the point in having all that knowledge if I have to spend the length of a kalpa to find anything?

They have different types of libraries. Obscure knowledge is Mora, but a mathematic examination of every particle in the universe falls of Jyggy

Mora has the better library but I bet nothing is in order. While Jygg who has severe OCD probably has all his documents, books ect organized by author, genre, numbers of pages, when it was written, hard cover or soft cover, and color of the cover.

Can Jygg really predict Sheogorath?

How I see it is that Jygg uses logic and calculation to determine the probability that something will occur. But Sheogorath's maddness allows him to be spontaneous and unpredictable. At times he would be too far removed from logic and calculation as to render Jygg's powers moot. Sheogorath, I believe, is one of the few who could actually deceive Jygg.