You wrote:
“The Church in Rome is not “the fullness of Christian truth.” As Paul himself wrote (see 1 Cor. 11:27, for example), the thing going into your mouth is not “flesh,” but “bread.” To agree with Paul is not heresy, is not falling short of “the fullness of Christian truth.”
May Rome decrease, and Christ increase.”
The Catholic faith is the fullness of truth. Nothing in the Catholic faith disagrees with St. Paul nor did St. Paul diagree with anything in the Catholic faith of which He was an Apostle. Christ is increased and He increases the Catholic Church.
In reference to the Lord’s Supper, Paul uses the term, “the bread” (see 1 Cor. 11:26-28). Here’s an example of his usage:
“For as often as you eat this bread and drink the cup, you proclaim the Lord’s death until he comes.”
Note that Paul says clearly that what you “eat” is not flesh, but “bread.”
The church in Rome discounts such a reference, instead saying that it’s literally the flesh of Christ, once again sacrificed, and that those who consider it (like Paul) to be “bread” are anathema.
I, for one, will believe the words of Paul in Scripture over the proclamations of the church in Rome. The church in Rome does not have “the fullness of Christian truth,” as shown.