3.) A little searching turned up exactly some of the purported Vetus Latina manuscripts which are said to contain the Comma:
Codex Speculum (m): A collection of statements and precepts (dated from the 5th century), drawn from Vetus Latina OT and NT. St. Augustine has been ascribed as the author, but this attribution is not likely. In Paul at least, the text seems to be generally more primitive than the European Latin of the bilingual uncials. In the Catholics meanwhile, it has many links with the text of [Priscillian, bishop of Ávila](Priscillian of Ávila). (Keep in mind that the earliest attestation to the Comma appears to be the 4th century Latin homily
Liber Apologeticus attributed to Priscillian or his follower Instantius!)
Codex Demidovianus (dem, 59): A now-lost manuscript of the Vulgate NT with Old Latin readings, containing text of the Acts of the Apostles, Pauline epistles, Catholic epistles, and Revelation, dating from the 13th century. Purportedly this manuscript contained the Comma. In the 18th century the manuscript belonged to a certain Paul Demidov Gregorovitch. The manuscript was passed on to his sons, but subsequently disappeared.
Codex Divionensis (div): Another lost Latin NT manuscript dating from the 13th century. Purportedly also contained the Comma.
Codex Perpinianus, aka Perpinianensis (p, 54): A 12th-13th century manuscript of the Vulgate NT with Vetus Latina readings, presently at the Bibliothèque nationale de France in Paris.
Codex Monacensis (q, 64): (Not to be confused with the Greek uncial
Codex Monacensis, aka X) From the 6th-7th century.
Out of these manuscripts, only Codex Monacensis and the
Speculum support the Textus Receptus reading. I quote from
the Catholic Encyclopedia article:
No Syriac manuscript of any family — Peshito, Philoxenian, or Harklean — has the three witnesses; and their presence in the printed Syriac Gospels is due to translation from the Vulgate. So too, the Coptic manuscripts — both Sahidic and Bohairic — have no trace of the disputed part, nor have the Ethiopic manuscripts which represent Greek influence through the medium of Coptic. The Armenian manuscripts, which favour the reading of the Vulgate, are admitted to represent a Latin influence which dates from the twelfth century; early Armenian manuscripts are against the Latin reading.
Of the Itala or Old Latin manuscripts, only two have our present reading of the three witnesses: Codex Monacensis (q) of the sixth or seventh century; and the Speculum (m), an eighth or ninth century manuscript which gives many quotations from the New Testament. Even the Vulgate, in the majority of its earliest manuscripts, is without the passage in question. Witnesses to the canonicity are: the Bible of Theodulph (eighth century) in the National Library of Paris; Codex Cavensis (ninth century), the best representative of the Spanish type of text: Toletanus (tenth century); and the majority of Vulgate manuscripts after the twelfth century. There was some dispute as to the canonicity of the three witnesses as early as the sixth century: for the preface to the Catholic Epistles in Codex Fuldensis (A.D. 541-546) complains about the omission of this passage from some of the Latin versions.
4.) Most sources I’ve read suggest the contrary idea to what this article is proposing: that the Comma is
absent from the Old Latin text(s) known to Tertullian, St. Cyprian, and St. Augustine.