You seem to be missing the point. Why should I pay any attention to John 14? Why should I pay any more attention to the "new testament" than to the "book of mormon?" Something tells me that you can't quite grasp the concept that the "new testament" isn't self-evidently true.
You are aware, are you not, that the Bible originally didn't have a "new testament," that it was added later? That's why it's "new."
You don't understand, do you? Your only defense of chrstianity is the quote the "new testament." You realize that only works with people who already believe in its authenticity?
I cannot help you in your unbelief. But, there is coming an event which will give you an opportunity to change your mind and call out ‘Blessed is He Who comes in the name of the Lord’. Don’t let your bitterness block your heart from repentence at that hour. Shalom