I afraid you haven't dealt with the object of discussion. You still have disagreement on the meaning and interpretation of Holy Scripture among those who say they are true believers.
Why should they take your word or your authority over theirs or someone else's?
That’s easy. If one does not use all of scripture while using scripture to interpret scripture with the guidance of the Holy Spirit one will not understand what scripture is saying. The problem enters when someone starts to rely on some “majesterium”, “council”, or other so called “authority” for interpretation. All error can be traced back to either relying on some “authority” outside of scripture or taking only portions of scripture then trying to fit other scripture into an erroneous preconceived idea of what they thought that original portion was saying.
Likewise, why should we take yours or the Catholic church's over someone else's?