Are we even on the same thread?
I expect so. We have before us the idea that there are three or more Abrahamic faiths. There can be only one, at most. It is true that Abraham may have been fictional, and there are
no Abrahamic faiths, but the people to assert that are hardly those who suppose that there can be
several.
The Christian claim is that true faith
started with Abraham, the first historical figure in the Bible, and that because he was justified by faith, and not works. The New Testament view is entirely in accord with that view of Abraham- and all other views are out of accord with it, as it happens. Those who take another view
may be correct, nevertheless, but the coherence and systematic unity of the whole Tanakh and NT have been the subject of intense scholarship at the highest level for five hundred years, since scholarship of that view was permissible, and cannot be merely dismissed, not with any intellectual credibility, at any rate.