I think you are still looking for some overarching truth under which all truth, including religious truths, will somehow fit.
As I see it, truth is impossible except within a model in which one can say "That is true" or "That is false." What is true in base ten mathematics is meaningless or not true in base three. What is true on a Mercator projection map is different from what is true on a globe. What is true in Einstein's relativity is different from what is true in Newton's system. Truth is therefore the sum total of all the true propositions in a particular scientific model or grid (this is the argument of Wittgenstein's Tractatus).
By the time of the Investigations Wittgenstein extended the use of true and false propositions to all sorts of models such as those of aesthetics, ethics, games of all sorts, and I would add alternative models of religion and ideology. That means that the current agreed model for say, doing physics, is only one of many truth grids that humans use to discuss and order their life in the world around them.
In that sense I am post-modern. There is a level playing field for all models (systems of truth), and we are left to choose which of them we want to engage in.
But you are right in pointing out that Jesus said: "I am the way,the truth, and the life. No one comes to the Father except through me" (John 14:6). In this text he is speaking of God's own plan for bringing many children to glory (Hebrews 2:10). In that model no one, but no one, will end up in heaven except through Jesus Christ. But of course we should not add that no one can make it to heaven unless he or she has the right doctrine or the right denomination. Young infants, retarded persons, and many others in all nations will be lovingly saved by the Son of God without ever understanding how he did it.
We are not saved by understanding some truths, or system of truth, otherwise the intelligent would make it and the simple-minded would be left behind.