The full rules of capitalization for English are complicated, and have also changed over time. To us, an 18th-century document uses initial capitals excessively. And you can throw all this into the air when it comes to languages like German, which have entirely different rules for capitalization, with different implications for meaning.
Therefore I would caution against reading too much into capitalization or lack thereof, by English Bible translators: your argument could be kaput in German.
And the consensus among biblical scholars is that all four canonical gospels were originally written in Greek. Where do you get the idea that John couldn't read or write Greek? This sort of statement makes me think you are getting your information from sources radically other than, and counter to, Catholic, Orthodox, and Protestant Scripture scholarship.
Who are your scholars? Can you link to a website?
>> “And the consensus” <<
.
Yes, like Global Warming.
The evidence, on the other hand is to the contrary in almost all of the books of the NT. Evidence of translation is strong. The consensus people had an agenda, and so did their Father.