I’m not sure you are right about “living water”, but you make a good point about “my food is to do the will of the one who sent me”. According to this mode of interpretation, “the flesh” of verse 63 may be a figure for unbelief.
In verse 63, Jesus is answering the concerns of His own disciples about the hardness of His saying about eating His flesh. This context indicates that verse 63 is a further explanation of His words. Jesus tells His disciples not to think that the eating of His literal flesh is what gives eternal life, but rather His words, which are spiritual (i.e., originating in the inspiration of the Spirit & applied to individuals by the Spirit), are what give eternal life.
In fact, Christ’s flesh does avail. Cf. Jn 6:51, Heb 10:20; Heb 9:11. Our bodies also avail as instruments of righteousness. Cf. Rom 6:13, 19; Rom 12:1.
Citing John 6:51 here is question-begging. Besides, as I already stated, you fail to take it as literally as you pretend, because Christ's body DID NOT come down out of heaven. Christ's body was created in Mary's womb.
Heb. 10:20, as I mentioned earlier, is speaking of Christ's atoning death, which is only effective because He took on the flesh & blood nature of a man; it is not speaking of literally eating His flesh & blood. Heb. 9:11-12 is indicating, again, that Christ's atoning death is what gives access to the heavenly tabernacle.
As for our bodies being instruments of righteousness, who disputed that? But this does not mean that human flesh, even the human flesh of Jesus, in itself gives eternal life!
Moreover, the continous history of the Church indicates a bodily interpretation.
The history of the church is not nearly so one-sided as you pretend. See "
The Eucharist," by William Webster.
Jn 6:51-8 are not fully explicit as to transubstantiation the way Justin and Irenaeus and Cyril are. Even Mark is more explicit than John on this point. Cf. Mark 14:22. However these verses in John are explicit that we must eat and drink Christ’s body and blood.
Mark 14:22 has nothing to say of transubstantiation. It is, once again, Jesus using a figure of speech. If the bread used in the Last Supper had transformed in that moment into Jesus' flesh, where did this flesh come from? Was it taken from somewhere inside Jesus' body? Was it newly created? Or was Jesus' body magically extended in time & space? Transubstantiation makes nonsense out of Scripture, & it also makes nonsense of the nature of the human body. Furthermore, Luke 22:20 militates against your interpretation of Mark, for Luke writes, "And the cup in like manner after supper, saying, This cup is the new covenant in my blood, even that which is poured out for you." This cup IS the new covenant! So, do you propose that in the Mass the cup in which the blood is contained is transubstantiated into the new covenant? Is the new covenant a physical object? It is clear that Christ was speaking figuratively.
Scripture says that Christ died once bodily on a Cross to redeem myriad souls and bodies by drawing all things to himself. Cf. Jn 12:42. I don’t know where the Scriptures say Christ’s Body cannot be in more than one place at once.
I'm not sure why you cite John 12:42. As for the nature of Christ's body, you will surely agree that His body is of like nature to our own bodies (albeit now glorified & incorruptible). But the nature of a human body - of any physical body, for that matter - is to be localized: it exists in only one place at any given time. If transubstantiation is true, then Christ no longer has a true human body, but something altogether different.
