You are absolutely right. The amount of mysticism in the Roman Catholic Church amazes me. That is the danger of avoiding sola scriptura. There is no objective standard by which these ideas can be measured.
Of course there is.
It should be noted that though many might write concerning Catholic truth, there is this difference that those who wrote the canonical Scripture, the Evangelists and Apostles, and the like, so constantly assert it that they leave no room for doubt. That is what he means when he says "we know his witness is true." Galatians 1:9, "If anyone preach a gospel to you other than that which you have received, let him be anathema!" The reason is that only canonical Scripture is a measure of faith. Others however so wrote of the truth that they should not be believed save insofar as they say true things. (St. Thomas Aquinas, Commentary on the Gospel of John 21)