Here's a whole array and examples of information on why Daniel isn't 2nd century:
The Date of the Book of Daniel
In addition,
The Jewish Historian JOSEPHUS [Antiquities, 11.8.5] mentions that Alexander the Great had designed to punish the Jews for their fidelity to Darius, but that Jaddua (332 B.C.), the high priest, met him at the head of a procession and averted his wrath by showing him Daniel's prophecy that a Grecian monarch should overthrow Persia. Certain it is, Alexander favored the Jews, and JOSEPHUS' statement gives an explanation of the fact; at least it shows that the Jews in JOSEPHUS' days believed that Daniel was extant in Alexander's days, long before the Maccabees.
And that's 332 BC and Daniel had to have been written even earlier than that for the Book of Daniel to have been in circulation.
What's more, linguistic studies of the verbiage found in Daniel indicates it coincides with the Aramaic of the fifth and sixth centuries BC.
"In fact, J. A. Montgomery points out that the "the very language of the story [of Daniel (4:30)] is reminiscent of the Akkadian" found on the Grotefend Cylinder. ["The Book of Daniel," ICC. Vol. 23 (1927): 243] The point here is that in the Akkadian "the verb normally falls at or near the end of the sentence" whereas in the normal Aramaic of Palestine it would not. [Kitchen (1965): 76] This point "proves that the Aramaic of Daniel (and Ezra) belongs to the early tradition of Imperial Aramaic (seventh-sixth to fourth centuries BC) as opposed to later and local Palestinian derivatives of Imperial Aramaic ..." [Kitchen (1965): 76; Soggin, 409] "
"A "linguistic analysis indicates that in morphology, vocabulary, and syntax" of the Aramaic of Daniel is considerably earlier (on the order of several centuries) than that of Genesis Apocryphon (1QapGen) and the Targum of Job (11QtgJob) which date from either the late 3rd or 2nd century B.C.. [Archer (1985): 23 and (1974) 471; see also Vasholz, (Dec 1978): 315-321; and his Ph.D. dissertation A Philological Comparison of the Qumran Job Targum and its Implications for the Dating of Daniel. (Univ. of Stellenbosch, 1976); and his "The Aramaic of the 'Genesis Apocryphon' Compared with the Aramaic of Daniel," New Perspectives on the Old Testament. Edited by J. B. Payne (1970): 160-169; Kutscher, "The Language of the 'Genesis Apocryphon,'" Aspects of the Dead Sea Scrolls. 2nd edition, (1965): 1-35; Kutscher, "Dating the Language of the Genesis Apocryphon," Journal of Biblical Literature, vol. 76 (1957): 288-92. More information on the Job Targum can be found in: T. Muraoka, "The Aramaic of the Old Targum of Job From Qumran Cave XI," Journal of Jewish Studies, vol 25 (1974) and S. A. Kaufman, "The Job Targum From Qumran," JAOS vol 93 (1973)] Collins notes that the Aramaic of the Qumran community was only in use between 200 B.C. and 200 A.D.". Therefore, since the Aramaic of Daniel is several centuries older than that of the Qumran community then Daniel had to have been written around 600-400 B.C.."
So, your 2nd century theory is a bust.