I don't know why He did or didn't actually give them his literal flesh and blood to consume. He surpasses me in every way. :)
We have the words and we are ever more convinced that He actually said and meant the words that He used because of the reaction of the Jews (who were aghast at the idea of cannibalism). It IS hard. You MUST believe. And you MUST participate in Communion with Him.
This isn't some obscure reference in some corner of the Epistles, this is a big deal with Jesus making His words very clear, meaning exactly what He said.
I don't understand how anybody could possibly interpret them in any other way than exactly as written.
And as to your second question, I believe that the answer is "yes."
mark for later
The praying to Mary, deification thereof, and praying to persons dead, but sainted by the Catholic church, for intercession are additions that contradict those scriptures.
Oral tradition is fine, so long as it is consistent with what is already written and sanctified, I would think.