You haven't highlighted any "problems." Your supposed "problems" are only "problems" if you insist on scriptural literalism. Since scriptural literalism is terrible hermeneutics, traditional Christian exegesis has never insisted on a literal reading of Scripture. As a formal methodology it is barely 100 years old, and as an informal approach to Scripture it originates in the Protestant reformation. Actually that was a huge part of Luther's problem with the Church: he thought the text should stand on its own and that ordinary people should have the ability to read and interpret it for themselves, instead of having to have the meaning of Scripture explained to them and mediated by the living tradition.
But just because I feel like it:
2) Jesus Christ, the purported son of God, was familiar with Isaiah and felt no need to identify the fraudulent sections.
3) Early church apostles and leaders did not identify the fraudulent sections.
4) From a Catholic point-of-view, the bishops at the Council of Laodicea when voting on which books to include did not spot the forgery.
You are making the mistake of assuming that because the author of Deutero-Isaiah is not the author of the rest of Isaiah, that it is somehow a forgery or a fraud. The author of Deutero-Isaiah was considered, both by the Jews of his era, and by the later Church Councils such as at Laodicea, to have been "divinely inspired." The point being, just because the author of Deutero-Isaiah is not the same as the author of the rest of Isaiah, that does not mean that he was not "divinely inspired."
Similarly, much of the Gospels were written, not by the actual Apostles named, but by their students and followers, in their name. In the ancient world, this was seen as a way of paying homage, of practicing humility, and (yes) of establishing authority. The idea is that you would write something in your teacher's name, in order to add to your teacher's reputation, and to draw on the authority of your teacher within the wider community. There is no reason to believe that the author of Deutero-Isaiah had any nefarious motives.
Now, it is true that Joseph Smith was a fraud with transparently nefarious motives, that the Book of Mormon is a fraud, and that the supposed author of the Book of Mormon is not the author that Joseph Smith claimed it to be. The Book of Mormon is a fraudulent document composed in the imagination of Joseph Smith. But you are missing the point that just because Joseph Smith was a liar and a fraud, that does not mean that the author of Deutero-Isaiah was a fraud.