We do not have the proofs today from the Apostle John; the earliest account that I have been able to find is from Gregory of Tours.
Legend "It is said" etc. Just doesn't cut it. Actual, proveable documentation from an eyewitness or, best yet, from the Apostle.
Agreed. Yet we are speaking of faith. If we found a letter from John that was proven (!) to be accurate and correct, would you then adopt the Catholic Faith?