You need to face the reality that unity has different levels and scope, and under each model unity as to one faith one Lord, one Faith, one baptism has been realized, but not universally or as meaning a comprehensive theology.
RCs differ among themselves about deeper aspects of each, while the EOs disagree with Rome about the One Lord as some aspects, and as to what the One Faith all entails, and the practice of baptism, but in essence they can profess to agree with Rome (but who can also say they worship the same God as Muslims).
Then there are other sola ecclesia groups who, like Rome, use the premise of supreme incontestable authority to interpret all the evidence they need as supporting their church, but who radically differ with both Catholicism and historical Protestantism.
Then there are multitudes under the SS model who hold to a Trinitarian one Lord, and one Faith as salvation by faith, not earned, and one baptism as signifying that faith in that Lord, but who can differ about deeper aspects.
Thus what you need to concede is that sola ecclesia has not produced what it seems you demands SS to do, which i do not argue it did, while the issue is which means of unity is most Scriptural - assurance based upon the premise of perpetual assured infallibility, or Scriptural substantiation.
If you cannot concede this, then we might as well be done with this.
And those who don't believe in the Holy Trinity, and those who believe in salvation by election and those who believe in more than one baptism, or, etc.
Thus what you need to concede is that sola ecclesia has
That'd be hard since there's no such thing as the doctrine of "sola ecclesia" . :)
If you cannot concede this, then we might as well be done with this.
I think we have reached an impasse. I sincerely thank you for your courteous discussion. God bless...