You wrote “The first and most obvious (i.e., verbatim) is Romans 15:16”
to be a minister of Christ Jesus to the Gentiles in the priestly service of the gospel of God, so that the offering of the Gentiles may be acceptable, sanctified by the Holy Spirit.”
I found that only about 1/2 of the bible translations use the word priest in that verse
Even your own Douy Rheims does not use it
Douay-Rheims Bible
That I should be the minister of Christ Jesus among the Gentiles
sanctifying the gospel of God, that the oblation of the Gentiles may be made acceptable and sanctified in the Holy Ghost.
So I suspect we are looking at different early sources..
But no matter the sourse the verse is clear that this is not about the “eucharist” .
.BUT the preaching of the GOSPEL in a faithful manner.. no mass or consecration noted here . Note he did not use the word “priest” as a NOUN he was not calling himself a priest but used it as an adjective to describe his service..
No where in the NT is the last Supper called a sacrifice my friend.
We are told to offer OURSELVES as a living sacrifice ..
That is very different than calling communion a sacrifice..
I offer my self as a sacrifice , I do not need a priest to offer me on his altar ..
That is why Peter noted that the saved are ALL priests because we offer ourselves and our mediator is Christ
Once more there is no role of priest listed for the New Church because the priesthood was a type of Christ fulfilled at the cross where He offered the FINAL sacrifice for sin and fulfilled the type