Does John 6 support the notion of having Masses here and now?

Roman Catholicism says that Jesus gave priests the power to celebrate Mass and turn bread and wine into his body and blood for the spiritual nourishment of the people. This doctrine is not in the Bible and is borrowed from pagan rites which aimed to help people consume their god.

John 6 however has Jesus saying he will give the world bread which is his flesh for the life of the world and unless you eat his flesh and drink his blood you will not be a friend of God and not permitted to rise again to enjoy everlasting life with God.

Have Catholics jumped the gun? Could it be that the feast of the flesh and blood of Jesus talked about in John 6 is not the Mass but what happens after death, a meal in Heaven?
 
Even if John 6 does teach transubstantiation, or at least somehow really eating the flesh and drinking the blood of Jesus, it still does not help the Catholic Church support it’s Mass.
 
Jesus might have offered us his body and blood under the forms of bread and wine now but he won’t give it to us until we are ready after death so that it makes our bodies immortal. God enables the person to eat this food and drink this blood at the resurrection. The words, “Whoever eats my body and drinks my blood has everlasting life and I will raise him up on the last day,” because of the present tense seem to say we can eat and drink them in this life. But it could be something like, “Whoever finds the fountain of life will live forever” meaning “Whoever finds the fountain of life that I offer now but which you will not be ready for until the resurrection will live forever”. It’s not saying any individual will find it but that it can and will be found.
 
The sentence could be “Whoever eats my body and drinks my blood has everlasting life (and I will raise him up on the last day).” This explains the awkwardness of the bracketed words. It opens the text to those who think that if you die in grace you get communion after even before the resurrection. Or the reference to raising might not be chronological.
 
You would wonder what eating Jesus and drinking his blood has to do with rising again. But if you take eating Jesus to mean taking the benefits of his saving death when he sacrificed his body and drinking to mean taking the benefits of his giving his blood it is explained. The notion is that you are saved in body and soul by Jesus making up for your sins and saving you from divine punishment including death. Another way to explain it is that you can only receive Jesus's flesh and blood if you are delivered from sin forever.
 
Jesus said, "and I will raise him up on the last day" and added "for my flesh is real food and my blood real drink." Again it seems that eating and drinking in this life can't have anything to do with Jesus raising people up. It is makes sense if you take it to mean a supernatural feeding on Jesus, flesh and blood, in the beyond.
 
The Church says Jesus was offering the Jews the Eucharist there and then if they would purify themselves of all sin. If he was then they won’t get it until they rise again as saints fit for Heaven and if they avoid Hell.
 
Jesus said that anybody who ate the bread of Moses, the bread that fell from Heaven in the wilderness eventually died. He contrasted it with his bread so whoever eats it lives. It means physical life as well as spiritual life or grace. Physical life seems to be the chief thought or it could be the only thought in the portion that is taken to be about Jesus becoming the Eucharist (v48-58). If the Eucharist gives you literal eternal life then you only get it after you die and the Eucharist of the Catholic Church is a counterfeit. The Old Testament texts never say that those who ate the manna lost their spiritual life forever. But they do indicate that they all died like everybody else.
 
Jesus didn't need to bring Moses or the manna into it at all unless he was on about physical and resurrected eternal life.
 
Even if we say only that it could mean physical life then we are saying we cannot prove that the chapter means transubstantiation. That would prove it could not mean it for it would be clear and would make it impossible to deny if it did. Transubstantiation is an unusual and strange idea. It is a very vague and difficult doctrine. It needs to be taught with extreme clarity. Jesus didn’t say, “God has the power to do anything. He can turn bread into flesh while it remains seeming to be bread.” Without this clarity we cannot assume Jesus taught the doctrine.
 
Thus there is no evidence in the Bible that Catholics should be offering Mass. John 6 forbids the Mass even if it teaches transubstantiation. It might be that when Jesus said at the last supper that he would not drink the fruit of the vine again until the kingdom of God comes that he was saying that there would be a Eucharist then and none from the time he spoke until then. John might have developed this idea into Jesus doing more than a Eucharist then but also doing a transubstantiation.
 
Some say that when Jesus said that if you eat his flesh and drink his blood (now) you will have eternal life (future) he was saying the food is available now and not just after death. But he could be speaking hypothetically.
 
The notion that you get utter union with Jesus after death reflects Paul's doctrine that when you are saved in Heaven God is all in all.

After Jesus said you have to eat his body and drink his blood to have eternal life we are told that many of his disciples grumbled against this. Naturally some of the non-disciple people there were complaining too. Anyway he says, “Does this offend you? Then what if you were to see the Son of Man ascending to where he was before? And the spirit gives life but the flesh cannot.”

Why does he not say, “See the Son of Man ascended to where he was before?” Then he would be seen in his glory. But no it is about his going up like a rocket. He could be going to Mars or anywhere. Why is rising up so important? And as he did not become the Son of Man until he was born where was he before? Those who think that John’s Jesus became man in Heaven and descended and so Mary was only his adoptive mother may have a point. He is telling them that they need a miracle, to see an ascension, before they will believe what he said.

He of course did not give them their miracle.  But he still demanded faith in what he said.  Strange.

Perhaps he would have to rise up to Heaven to give them a Mass in Heaven?
 
John 6 gives no authority to the Catholic Mass. It forbids it. It is a counterfeit of the real Mass of Heaven.