Why not go back to the source, to that 1st Century Apostle, Apostle Paul? ...Take for instance (in Rom 11) his example with the wild shoots (gentiles) and natural shoots (Abraham's offspring through Isaac); Paul interplays them never confusing them or even having one replace the other. He even warns the gentiles about any boasting of 'branches being broken off that I may be grafted in'...sounds like some sort of replacement idea to me.
Prism, you misunderstand the early fathers and the value they give as a protection against apostasy. They are placed as foundations so near to the Apostles as teachers of the Church. I don't know how you could make your judgement that they “were full of disagreements amongst themselves”. What are you talking about? It doesn’t sound like you know the subject at all. Where is your evidence for such a statement? It seems to me that the only apostasy is the falling away from the teaching that the Church is the “Royal Priesthood”. (Exodus 19:6; 1 Peter 2:9).
Paul is equally misrepresented in Roman and Galatians. I would be happy to discuss these scriptures in another thread step by step so everyone can be brought back from these “Jewish Myths” (Titus 1:14).