Augustine as I read him was talking to the Jews who were merely looking for food to eat that was of this world. So before he got to the notion of the Mana from heaven that God gave the ancient Jews thru Moses, he first had to challenge them that belief in him was essential and the first step before getting into the Eucharistic notions of the bread of life discourse. So on the Point where Saint Augustine is pointing out that Christ was trying to get the Jews to belief in him, once one believes, then the Eucharist becomes the next discussion and for believers, the Eucharist becomes the fullfillment of the mana in desert, so just as God gave the ancient Jews Mana to feed them in the desert on their journey from liberation from Egypt to the promise land, Christ sustains the believer with the sacrament of his body and blood during our journey from Baptism to our death when we will meet the Lord face to face.
Saint Augustine and Fr. Bartunek are making different theological points and while they are different they are not opposed to each other. I 1) Believe in the Holy Trinity [Faith in God] and 2) believe that God sustains me via the Eucharist.
This is merely your faith pretending that Augustine is speaking in one way, and then reverts to some Transubstantiation language later, when none exist. You are imagining things. You are dreaming and hoping. If transubstantiation is true, and John 6 is a proof text, then Augustine would cite the same verses to give a "different" reading. He never does, but in fact doubles down on this interpretation throughout his tractes. You cannot make assertions like this without providing some kind of argument.
Augustine is quite clear in explaining how it is the Jews may "obey the precept" that Christ commands, and this Augustine says is obeyed by believing, without use of "teeth and stomach." If that is not how the precept is obeyed, then Augustine is either wrong or telling lies. One cannot then read the same text and then claim that "teeth and stomach" is mandated by Christ using the same precept. You are merely making an assertion without engaging in any analysis of what the text actually says. This, again, is just your catholic faith speaking, which molests not only the scripture, but even the church fathers too.
As I read the BIBLE, they asked Him a DIRECT question and He gave them a DIRECT answer.