Your assertion that the NWT rendering of John 1:1 as "the Word was a god" is grammatically correct is not supported by most reputable Greek scholars.
Yes the rendering “a god” is supported by some of the most reputable scholars such as Adela Yarbro Collins, one of the most respected biblical scholars around. Even Trinitarian scholars who do not support the translation have admitted it is grammatically correct but do not support it on theological grounds.
Scholars who argue for a qualitative understanding of "theos" in John 1:1c emphasize that John was identifying the Logos as fully divine, not as one among many lesser gods.
Jesus himself indicated that he is a lesser God than his Father because he stated that his Father is the only true God in John 17.3, and in John chapter 10 he justified his own limited divinity by pointing out that creatures are called gods in Psalm 82. That’s an odd argument to make unless Jesus was clearly indicating that his divinity is on a level with other creatures and less than God almighty.
You argue with Robert Kraft that nomina sacra, “originated among Jews and was taken over and elaborated by Christians”. You also argue with Larry Hurtado that nomina sacra, “likely began with the abbreviation of the name of Jesus and then expanded to include other key titles, such as ‘Lord’ and ‘God.’” You do realise that those propositions contradict each other? Because, obviously, if Jews originated the practice of nomina sacra they would not have started with the name ‘Jesus’, and conversely, if the first nomina sacra was ‘ Jesus’, then obviously the practice originated with Christians, not Jews. So which are you actually arguing for?