I find your take quite interesting. At the same time, I am not at all certain we are very far apart. In fact, I suspect each of us has hold of a piece of a single garment. That being said (and meant), I want to respond to a few matters.
Like you, and the majority of modern western thinkers, I resist herd mentality in favor of radical individualism, by which I tend to mean a kind of lonely and responsible individualism. We always enter the narrow way alone, if we enter it at all.
Once on that way, though, I think we may well find others walking it as well. This is a new community in the making, made up of individuals who share the experience of entering through the narrow door and walking the narrow way. At this point it is not so much that we are coming to God as that we are walking with God. Strangely enough, there's room on the way for all those who choose to walk there.
Walking is a key term. Those who find and walk this way may well not share a language, culture or era. They may well have quite different concepts of God and very different belief structures as well. But they find themselves walking the same road, and over time they find they share a deepening commitment to continuing to walk, helping one another, and even coming to care for one another.
Strangely, and sometimes to our aggravation, the narrow way combines radical individualism with community.
Now for some particulars. Your take on the Prodigal Son is apt, insofar as it goes. The beauty of a story, even a parable, is that it offers many sides for our inspection. I certainly agree your take is real and powerful. If we start with the end of the story, it makes sense. Does it grasp all the possiblities in the story? I do not think so. It seems to me that the prodigal could well have found his way without leaving home, but he did not choose to do so. Had he done so, his personal story would have played out differently, and his way to God would have been easier, at least with regard to physical, economic and emotional suffering. Either way required that he accept his father's love as a free gift.
Repentance or metanoia has never been about a creed or set of beliefs, though at any time strands within Christianity act as if it were so. Metanoia means to turn around and look a different way, walk a different direction, put on a different mind, and the like. Paul, in his better moments, saw this rather clearly. When we do so we increasingly see life with the perspective of Jesus and live accordingly. What that means for each follower, Christian or otherwise, must be discovered and fashioned as a individual. Again, though, as we do so we often find a community of others who share the perspective and the journey.