When viewed from the belief that Joseph Smith was not a prophet and the Church of Jesus Christ of Latter-day Saints is false, or that the Bible is perfect and unchanged from the day it was written1, the only conclusion is that Joseph was writting himself into history.
When viewed from the belief that Joseph Smith is a prophet and the Church of Jesus Christ of Latter-day Saints is true, the only conclusion is that Joseph restored a portion of the Old Testament that had been lost. A portion that supports his claim of being a prophet of the Lord.
Remember that we believe the Bible is not perfect. That over the course of time information has been lost (whether deliberately or by virtue of translation, it doesn't matter). We learn from the Book of Mormon, 1 Nephi 13:25-26 (my emphasis):
Wherefore, these things [the Bible] go forth from the Jews in purity unto the Gentiles, according to the truth which is in God. And after they go forth by the hand of the twelve apostles of the Lamb, from the Jews unto the Gentiles, thou seest the formation of that great and abominable church, which is most abominable above all other churches; for behold, they have taken away from the gospel of the Lamb many parts which are plain and most precious; and also many covenants of the Lord have they taken away.
1 Nephi chapter 13 is actually a lengthy prophecy. It makes for an interesting read. But, to specifically answer your questions:
(1) No, it specifically refers to Joseph Smith.
(2) The passage is something that God wanted Joseph to include.
(3) Nope, that's it.
1 If you want to discuss how perfect the Bible is, talk to a Jew. The Jews have a strong opinion about the quality of Christianity's Old Testament, but that's an answer for another question.
EDIT: After reading Luke's comment I wished I hadn't included my footnote as it doesn't actually add anything to the conversation. But, I'm kinda stuck with it... so I popped over to Judiasm.SO and asked them what they thought.
The most voted answer begins with the statement, "KJV may give the general sense of a translation in most cases. It definitely has a Christian bend and does not always follow the Jewish traditions in translation." It then provides a number of illustrative examples, including Isaiah 7:14, which illustrates the reason I included the footnote.
The Hebrew word for "virgin" isn't used in the original text. The word that is used is most commonly translated "young girl." Does this upset my faith? Of course not. But if King James' monks, who I do not believe had authority from God to translate His word, can't be trusted not to bias their translation in favor of their preferred belief, neither can anyone else who does not have, as I believe, authority from God to do so. From Joseph's journal (today referred to as the "Documentary History of the Church or DHC) we read:
From sundry revelations which had been received, it was apparent that many important points touching the salvation of man, had been taken from the Bible, or lost before it was compiled. (DHC, vol. 1, p. 245.)
I believe the Bible as it read when it came from the pen of the original writers. Ignorant translators, careless transcribers, or designing and corrupt priests have committed many errors. (DHC, vol. 6, p. 57.)
I stand by my footnote, despite wishing I hadn't included it, with one exception. I should not have boldly used the word "strong."