15 -Sefer Daniel was written long after the Jews returned from Bavel.Michael, let's leave aside your point about Amalek because here you are correct: How to define Amalek is entirely a halachic question, and one properly left to Rabbis. (who, incidently, are divided: They say the term "Amalek" may be used to refer BOTH to an ancient, and as such currently unidentifiable, desert tribe, AND a certain viewpoint or state of mind that may exist among people in the modern world. This is something Orthodox Jews should know.)
23 - Amalek is a state of mind and not a race.
14 - Moshiach appears no where until Sefer Daniel.
In addition to techiyas hameisim that has already been mentioned, the above three points are not within the normative Judaism. [sic]There is no Jewish authority that has respect for halacha that claims that there are no references for Moshiach before Sefer Daniel. Sefer Daniel, according to the Gemoro, was entered into the Canon by Ezra, and those who claim that it was written later claim that it was written well after the Greek Conquest, which was after the death of Ezra. So, normative Jewish thought rejects this idea. Halacha assumes that Amalek is a tribe, and that Jewish kings have a Mitzvah to lead the people in a war of annihalation against them.
Your point about Daniel, though, is a category error. "Judaism" must stay silent about when Daniel was written, because this question relates not to halacha, but to history. If the consensus among scholars is that Daniel was written during the mid-second century BCE Judaism must yeild to their judgement, in the same way that it yields to the judgment of doctors and scientists. Our Rabbis don't have the tools -by which I mean training and experience- to disagree. A claim that has been disproven must be set aside, and and the case has been made to my satisfaction (not to mention the satisfaction of legitimate scholars) that at least parts of Daniel were written after the Hellenistic conquest. This is also something Orthodox Jews should know.
As for whether or not references to Moshiach appear before Daniel, this objection splits the difference. It's not a halachic question, but Rabbis are certainly qualified to judge where ideas make their first appearances in the canon. However, unlike the two previous issues, scholars and Rabbis stand on equal ground when it comes to evaluationg questions of this nature.