That's because the verb "is" is not used in a mathematical sense, which would require that the word "Scripture" and the words "Jesus Christ" would be interchangeable: if so, one could say, for instance, "Scripture died on the Cross." This is an absurdity based on the mistake of thinking that "is" in this context means "identical."
Scripture is not of couse, "just" a mere book like any other. Its principal author is God. It contains supernaturally revealed truths. It is the Word of God in the words of men.
But "Scripture" did not die for my sins; and I could be a destitute illiterate with no contact with "Scripture," but he saved by the redemptive work of Our Lord Jesus Christ.
This is why it is hard for you to take it in to your life. Because you believe there are other authors than God. For if you say He is the "Principal Author", then there are others according to this thought. I suspect the others are your Popes and Authorities. Therefore it is really hard for you to trust it.
The Lord Jesus Christ said John 6:57 "As the living Father sent Me, and I live because of the Father, so he who eats Me, he also will live because of Me". You believe this is refering to what you call the "Eucharist" .
We call it Eating the Word of God, and living being tranformed (Romans 12:1,2) by God. Not just once in a while. This is how I eat Him and live in Him as much as possible. The results are Three times the Love (John 15:21 "He who has My commandments and keeps them is the one who loves Me; and he who loves Me will be loved by My Father, and I will love him and will disclose Myself to him."
This I testify is true and that "Love is of God" just as the Apostle John said in 1 John 4.
The weak view of the Scriptures makes it hard for you to EAT HIM this way. You have to worry about all the different Authors just as you have said.
Whereas for me, there is only ONE AUTHOR of SCRIPTURE, ONE WHO INSPIRED IT, ONE WHO BRINGS IT TO PASS, ONE WHOM I EAT and ONE who is Worthy to be called "THE WORD MADE FLESH" - The Lord Jesus Christ Alone.