"Do you actually read your own prooftexts?"
Actually it is reading the whole of scripture not just one verse. Here is how Jesus looks at how the Pharisees use tradition to interpret scripture. (Mar 7:13) "Making the word of God of none effect through your tradition, which ye have delivered: and many such like things do ye."
Now if you understand that you can see understand what He is saying in John 5:38-40, "And ye have not his word abiding in you: for whom he hath sent, him ye believe not.
Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me. And ye will not come to me, that ye might have life."
Why would they not come to Him, because their tradition laden interpretation of the prophecies would not permit it.
I understand that your latest interpretation comes from this context, and don't disagree with it. However, in 5887 you said about John 5:38-40 "Jesus says it is through the scriptures that we have life, not tradition." This is not correct, and this is what I object to. John 5:38f does not say that we have eternal life through the scriptures.