Penna, John 6 follows the feeding of the 5000, as I am sure you know. The reason they followed him was because they had eaten their fill of the loaves, not because they saw a miracle. They were interested in the material gains they could make by following him. Jesus' whole point in this discourse was to demonstrate they did not understand spiritual things because they were not his. He did not call the confounded Jews back to correct them because the reason he said what he said was to confound them. Why? Because their heart was set on the things of the flesh. material gain. His disciples who remained would understand in time that the bread refers to his body that was broken on the cross and his blood refers to the blood that was poured out for us on the cross.
Luke 22:19-21: "And he took bread, and when he had given thanks, he broke it and gave it to them, saying, 'This is my body, which is given for you. Do this in remembrance of me.' And likewise the cup after they had eaten, saying, 'This cup that is poured out for you is the new covenant in my blood."
This explains the speech in John 6, so contextually and cotextually we understand that Christ is not talking of a physical consumption of his flesh or a re-enactment of his salvific death on the cross, indeed Christ cannot be crucified over and over as Paul says in Hebrews 6: 4-6 "For it is impossible, in the case of those who have once been enlightened, who have tasted the heavenly gift,and have tasted the goodness of the word of God and the powers of the age to come, and have shared in the Holy Spirit,and then have fallen away, to restore them again to repentance, since they are crucifying once again the Son of God to their own harm and holding him up to contempt." This rules lout even the possibility of transubstantiation. Hence, communion is a symbolic remembrance. The text does not support the Catholic position.
Matthew 16:18-19 is not affirming that Peter is the new infallible pope of his Church. For one, if that was so, how could Jesus rebuke him in the very following verses? Further to that point, Paul publicly corrects Peter in Galatians 2:11-14? He was also sent to Samaria by other apostles in the book of Acts 8:14. Simply put, Christ never gave Peter any more authority than any of the other apostles.
Again, Penna, I am afraid you've fallen for a deception.