I am not a Greek scholar and I can’t prove that Rev 3:14 means that Jesus is God’s first creation. But I think it is reasonable to point out the high quality of academic support for understanding this verse to mean that Jesus is God’s first creation.
Top lexicographers responsible for the Bauer, Arndt, Gingrich, Danker Greek lexicon say that “first created” is the probable meaning of the word arche in this verse. They are aware of the range of possible meanings and they select this as the most likely. They also cite an example from the Septuagint where the creature behemoth is described using the same phrase.
Plus, in terms of the academic study of the apocalyptic genre, scholars hardly come more senior in the field than John Collins and Adela Yarbro Collins. They are professors are Yale and Adela Yarbro Collins is past president of the Society of Biblical Literature. They have published some of the most respected and widely cited academic publications on the topic of apocalyptic literature. What is their take on the identity of Jesus in the book of Revelation? They write:
In the light of the evidence that the author of Revelation portrays Jesus as the heavenly messiah who is also the principle angel of God, these sayings are best interpreted as associating Jesus with personified wisdom as God’s first creature … In Revelation the evidence suggests that he is God’s first creature, namely, the principle angel.
John J. Collins and Adela Yarbro Collins (2007). King and Messiah as Son of God: Divine, Human, and Angelic Messianic Figures in Biblical and Related Literature, page 203.
Just because senior scholars in the field happen to support the JW understanding of this particular point obviously doesn’t prove they are correct. At the same time it does seem reasonable to note that the JW reading has impressive academic support here and is at least a legitimate and reasonable way of understanding the text.