I do not know if he ever considered them NOT part of Scripture. He was from Alexandria, where the Septuagint was written. Which answers your second question. The Septaugint of the New Testament era contained the Deuterocannonicals, since earlier Church Fathers quote from them as if they were Scriptures.
But I am also sure that we all realize that citing Origen as authoritative on anything is fraught with errors as he was a well known heretic and corruptor of the texts of the scriptures.
Origen obviously had a high respect for Scripture, just by the fact that he wrote the Hexapla. While he had some heretical views about the pre-existence of the soul and whether hell was populated with men or not, that doesn't have a bearing on his opinion of what the Church considered as Scripture. He was probably one of the greatest exegisist on the Scriptures the Church had known for the first 1000 years.
Regards
"We have now to speak of the labours of ORIGEN in connection with the text of the Septuagint. This learned and enterprising scholar, having acquired a knowledge of Hebrew, found that in many respects the copies of the Septuagint differed from the Hebrew text. It seems to be uncertain whether he regarded such differences as having arisen from mistakes on the part of the copyists, or from errors of the original translators themselves.
"The object which he proposed to himself was not to restore the Septuagint to its original condition, nor yet to correct mere errors of translation simply as such, but to cause that the Church should possess a text of the Septuagint in which all additions to the Hebrew should be marked with an obelus, and in which all that the Septuagint omitted should be added from one of the other versions marked with an asterisk. He also indicated readings in the Septuagint which were so incorrect that the passage ought to be changed for the corresponding one in another version.
"With the object of thus amending the Septuagint, he formed his great works, the Hexapla and Tetrapla; these were (as the names imply) works in which the page was divided respectively into six columns and into four columns.
The Hexapla contained, 1st, the Hebrew text; 2nd, the Hebrew text expressed in Greek characters; 3rd, the version of Aquila; 4th, that of Symmachus; 5th, the Septuagint; 6th, Theodotion. The Tetrapla contained merely the four last columns.
"Besides these four versions of the entire Old Testament, Origen employed three anonymous Greek versions of particular books; these are commonly called the fifth, sixth, and seventh versions. Hence in the parts in which two of these versions are added, the work was designated Octapla, and where all the three appeared, it was called Enneapla.
"References were then made from the column of the Septuagint to other versions, so as to complete and correct it: for this purpose Theodotion was principally used. This recension by Origen has generally been called the Hexaplar text. The Hexapla itself is said never to have been copied: what remains of the versions which it contained (mere fragments) were edited by Montfaucon in 1714, and in an abridged edition by Bahrdt in 1769-70.
"The Hexaplar text of the Septuagint was copied about half a century after Origen's death by Pamphilus and Eusebius; it thus obtained a circulation; but the errors of copyists soon confounded the marks of addition and omission which Origen placed, and hence the text of the Septuagint became almost hopelessly mixed up with that of other versions."
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I find it interesting that Origen was not trying to correct the Hebrew text in the 1st column of his Hexapla in order to make it read more like the Septuagint in the fifth column, but vice versa. He clearly believed the Hebrew text that he had in his first column was accurate and authoritative, but that all the other Greek translations in his hand, including his LXX, to be flawed and in need of revision to be brought more in line with the Hebrew of column one.
I wonder if the Hebrew text in Origen's first column was the same as the later Masoretic text.