I don't intend to post a treatise on the subject in this setting, but I would be willing to bet that a google search of Apocrypha will provide significantly different results and authors than a search of deuterocanonical. That exercise will only prove that unbiased research in the context of sectarian disputes is a very rare commodity (your site included).
It should be noted that St. Jerome's belief was that only the original version of any Scripture was inerrant and in this context he pursued the Hebrew Old Testament as the most authentic. He did not contend, like Luther later did, that the lack of extant copies invalidated the deutercanonical books.
I am not at home so I don't have access to my personal library but I do have "numerous" citations, both directly from St. Jerome (Eusebius Hieronymus) and indirect by those referring to him. I am sure that your penchant for research will enable you to locate them if you have a desire to pursue unbiased research.
Peace be with you
While RCs attributing lack of objectivity or fair motive is usually one sided, yet I have done much searching which included both sides (i was looking at more than one Catholic answers [though they quickly banned me a while ago] page even today before this) , and it is unbiased research that is lacking among Internet RC apologists, and which therefore results in much countering evidence.
For rather than an unbiased treatment, and contrary to more scholarly sources (including the CE with its own slant), they abound with the lie that the canon was settled until Luther as a maverick questioned and rejected books, even if he did not say he considered his opinion the last word.
And here on this thread we have exampled the lengths some will go to in avoiding a simple admission of that fact.
I am not at home so I don't have access to my personal library but I do have "numerous" citations, both directly from St. Jerome (Eusebius Hieronymus) and indirect by those referring to him. I am sure that your penchant for research will enable you to locate them if you have a desire to pursue unbiased research.
I have, and which is referenced and responded to by another, but the issue is not whether Jerome invoked them in his polemics and even inferred or referred to some as Scripture, i believe the mistake that is made is not recognizing the two fold type of canon that was held, unlike in Trent (Deuterocanonical itself comes from the Greek meaning 'belonging to the second canon"). In which some were referred to as "ecclesiastical" rather than "canonical" or "apocryphal" -- they are read in the church, but not to be cited for proof texts of doctrine. ("Against Rufinus")
Thus while Jerome can be shown referencing DCs as Scripture, it is a matter of interpretation as to whether this amounted to an affirmation of unquestioned full divine inspiration on his part, contradicting his earlier claim.
The judgment of Catholic Encyclopedia in this regard is that,
An analysis of Jerome's expressions on the deuterocanonicals, in various letters and prefaces, yields the following results: first, he strongly doubted their inspiration; secondly, the fact that he occasionally quotes them, and translated some of them as a concession to ecclesiastical tradition, is an involuntary testimony on his part to the high standing these writings enjoyed in the Church at large, and to the strength of the practical tradition which prescribed their readings in public worship.
Obviously, the inferior rank to which the deuteros were relegated by authorities like Origen, Athanasius, and Jerome, was due to too rigid a conception of canonicity, one demanding that a book, to be entitled to this supreme dignity, must be received by all, must have the sanction of Jewish antiquity, and must moreover be adapted not only to edification, but also to the "confirmation of the doctrine of the Church", to borrow Jerome's phrase. (Catholic Encyclopedia, Canon of the Old Testament; http://www.newadvent.org/cathen/03267a.htm)
And it is one thing to argue that that he simply "knew of no Jews who considered the Deuterocanonical books as a part of Jewish canon or Scripture," as you state, and it is another thing to argue that and it is another to concede that he rejected them but argue that he later seemed to accept them.
That Jerome did reject them is what is to be unquestioned, based upon his unquestioned statements in his translations, such as his Prologue to the Books of the Kings: "...so we reckon twenty-two books, by which, as by the alphabet of the doctrine of God, a righteous man is instructed in tender infancy, and, as it were, while still at the breast."
This preface to the Scriptures may serve as a helmeted introduction to all the books which we turn from Hebrew into Latin, so that we may be assured that what is outside of them must be placed aside among the Apocryphal writings.
Wisdom, therefore, which generally bears the name of Solomon, and the book of Jesus the Son of Sirach, and Judith, and Tobias, and the Shepherd [of Hermes?] are not in the canon. The first book of Maccabees is found in Hebrew, but the second is Greek, as can be proved from the very style. http://www.bible-researcher.com/jerome.html
In his preface to Proverbs, Ecclesiastes, and the Song of Songs he also states,
“As, then, the Church reads Judith, Tobit, and the books of Maccabees, but does not admit them among the canonical Scriptures, so let it read these two volumes for the edification of the people, not to give authority to doctrines of the Church.” (Shaff, Henry Wace, A Select Library of Nicene and Post-Nicene Fathers of the Christian Church, p. 492)