I am no expert on the Reformed position myself, not considering myself a Calvinist or Reformed.
You’ll have to get that information somewhere else.
For my part, I believe that it’s strictly a memorial, with the elements representing the body and blood of Jesus. The clear Scriptural prohibition against eating blood makes that interpretation of it representing fit more readily with the rest of Scripture. There is then no conflict with other passages.
As far as the presence of Jesus, I find Scriptural support for the belief that Jesus indwells the heart of every believer already, when they surrendered to Him and were born again, and that as He said, where two or three are gathered together, that He would be in their midst.
I was bringing our primary petitions to be filed with the New Hampshire Secretary of State's office. As I approached the state capitol steps, I noticed three very clean cut young people sitting on the steps, a young man in a nice buckskin jacket and two well-dressed young ladies. I also noticed then Maine Senator and Democrat POTUS aspirant Ed Muskie approaching the steps. I waited to give Muskie plenty of space to go first.
The three young people, recognizing Muskie, got up on their feet and the young man confronted Muskie politely asking whether he was "born again" and whether he had accepted Jesus Christ as his personal Lord and Savior. Muskie, a Catholic of Polish ancestry, looked a bit confused. I suspect that was the first time that he (or I) had heard the term "born again." He recovered, pointed out that he was Catholic and that, of course, Jesus Christ was his personal Lord and Savior and then asked: "If not Jesus Christ, who could possibly be my Lord and Savior?"
In public life, Muskie was not really much of a Catholic, just a standard issue liberal on matters economic and increasingly on foreign policy with little in the way of social issue conservatism to recommend him. Yet, I believe that Muskie's response to the young man was a very normal Catholic response and a valid one.
I have been baptized (born again of water and the Spirit) as an infant according to the rites and customs of the Roman Catholic Church. The vows taken for me by my Godparents were also taken by me personally when I was 13 years old at my Confirmation before God and before then Hartford Archbishop Henry J. O'Brien. I have come to believe that our Catholic sacrament of Confirmation is a completion of our Catholic sacrament of Baptism. I believe that infant baptism draws objections from some Christians in that it is not a personal commitment by the infant who is being baptized and our Catholic answer is the repetition of baptismal vows by the one who has been baptized and now takes those vows personally having attained sufficient age.
As to my use of the term "Reformed," it is my attempt to be respectful. There are many Christians who are not Catholic by affiliation. I was brought up to reference all but the Orthodox as "Protestants." Some of my non-Catholic pro-life clients suggested to me that "Protestant" is not a useful term. Many preferred to be known merely as "Christians" and I had no doubt that they were Christians but there also seemed to be a suggestion that Catholics and Orthodox were not Christians in their understanding. I am a Catholic and respectful of others but I am not prepared to accept the idea that Catholics and Orthodox are not also Christian.
In short, as a Catholic, I struggle with myself and my own sinful nature to show well-earned respect to soldiers of Christ who are not of the Catholic or Orthodox fold and calling them by whatever truthful name they wish to be called while simultaneously insisting on the Christianity also of Catholics and Orthodox.
Sometimes I stumble in that effort but never intentionally. I also strive never to suggest that there are not important distinctions between Catholics (and among Catholics), Orthodox, Lutherans (and among Lutherans), Anglicans, Methodists, Congregationalists, Presbyterians (and among Presbyterians), Baptists (and among Baptists), Evangelicals, Pentecostals and many others whom I am failing to recall. My favorites are Missouri Synod Lutherans, Wisconsin Synod Lutherans, Westminster Confession Presbyterians, Southern Baptists, and some or most Evangelicals.
As a matter of history and Apostolic Succession, the Catholic (and possibly the Orthodox) Church were the original Christian churches tracing all the way back to Jesus Christ and his selection of twelve apostles (the original bishops). Later, the term Apostle is used more loosely when Jesus Christ was no longer physically present to choose more Apostles. Thus Saul who became Paul is referenced as an apostle and certainly that is the reality of his life of evangelism and death by martyrdom. Of the original twelve, Judas betrayed Christ and ten (not John) were martyred. We regard our bishops as literal successors of the twelve. Unfortunately we are all too aware that some are successors of Judas.
Thank you again for all that you do here. May God continue to bless His faithful servant metmom and all of hers.