“How do you separate the spoken words of Christ from the Scripture?”
I do not think it is necessary to do so. Jesus is the embodiment of the Scriptures.
Did Jesus say thing which are not recorded? Doubtlessly. But listen to John...
“Now Jesus did many other signs in the presence of the disciples, which are not written in this book; but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.”
The things that Jesus said which are recorded, were recorded specifically so that the reader may believe and have eternal life.
Everything we need to know to be saved and live eternally with God is in the Scriptures.
Simple isn’t it?
Read the book.
I marvel at the miracle of the Scriptures. I believe in the inerrancy of the Bible, and in God’s ability to protect his Word through time.
It brings me comfort to know that I can read the words of Jesus today, many those same words that he used when speaking to those closest to him.
I envy them because they knew him personally in human form. That must have been one of the greatest blessings of all.