“Mormons don’t believe Jesus is eternal.”
I would call that statement false, and you provided a source.
The Eternal God is not called by that name in error. If He is eternal and we are his children, what can be then said of us, much less his only begotten Son in the flesh? We are as eternal as The God of Abraham, Isaac, and Jacob. I don’t think getting all wrapped up in the word created will lead to clear thinking because what we know about creation in the eternal sense is really nothing.
“Mormons believe that there are in fact four sources of divinely inspired words, not just one.”
Also a false statement. Members of the Church of Jesus Christ believe there is but one source for divinely inspired words just like the rest of the Christian world. That source is God the Father. One notable difference might be the mistaken belief that God’s lips are sealed and the Bible must remain as the only source for his words, which would be inconsistant with God’s relationship with man from the beginning.
“They also adhere to books other than the Bible.”
Not so sure adhere is appropriate, but we are attentive to every word that comes from the mouth of God the Father and his son Jesus Christ. He has never proclaimed his sudden inability to speak for himself ever and since he is the same yesterday today and always we take him at his word.
That should be enough for now. I would suggest that anyone interested in the beliefs of any church would be wise to go direct to the source rather than give credence to a biased source with an axe to grind. That would be true in regards to Catholics, Protestants, Jews, LDS, etc., etc. Unless of course you are only there to hear what someone else thinks you ought to hear.
Mormons believe that there are in fact four sources of divinely inspired words, not just one: 1) the Bible “as far as it is translated correctly” (8th Article of Faith). Which verses are considered incorrectly translated is not always made clear. 2) The Book of Mormon, which was “translated” by Smith and published in 1830. Smith claimed it is the “most correct book” on earth and that a person can get closer to God by following its precepts “than by any other book” (History of the Church 4:461). 3) Doctrine and Covenants, containing a collection of modern revelations regarding the “Church of Jesus Christ as it has been restored.” 4) The Pearl of Great Price, which is considered by Mormons to “clarify” doctrines and teachings that were lost from the Bible (Articles of Faith, p. 182–185) and adds its own information about the earth’s creation.
https://www.gotquestions.org/Mormons.html
Sources from Mormon publications were provided. IF these are in error please clarify.