This is also intended quite literally. For how can one be guilty of profaning the body and blood of the Lord by engaging in merely a symbolic act.
This makes clear the need for confession for grave sin (i.e. violation of 10 commandments), true sorrow for our sins, penance, and forgiveness.
Thus, all of your other concerns regarding faith and conditions to be saved, are addressed.
The rest of your questions are simply the same as those expressed in verse 60, and you are unwilling to accept the words of Christ.
Do you follow Jewish dietary laws? No? Because we are no longer in that dispensation.
Grave sin? Is there any other kind? One sin will put you into eternal damnation without faith in Christ. How more grave do you need it?
The disciples found his teaching to be difficult to accept because of lack of faith? You are writing an interpolation. It doesn't say that. They couldn't UNDERSTAND the metaphor, which Christ had to explain, thus, repeating the normal pattern in which Christ had to explain because he spoke in parables so that the religious leaders could not understand.
As for 1 Cor 11- the Lord tells the purpose for the supper: to remember and show His death. It isn't a salvation issue.
Eating the supper unworthy, what does that mean? What standard do you ascribe to it? What standard could it be for broken sinners? There are only two possibilities: (1) non-Christians, and (2) unrepentant sinners.