Hi Joe, great and intuitive questions. The problem of conversion is actually the central problem my research attempts to address. I've developed a 'narrative climax model' to explain the conversion experience. Perhaps I'll write about this in the future. Conversion experiences aren't 'bad' - at least not in the sense when we say murder is bad.
The latter concerns relativism. It's always a consequence of any postmodern theories about meaning, including this one. I honestly have no good answer at the moment. But if we see each person's faith as part of their story, then we can at least admit there are good and bad stories. Just like how there are good and bad story books. Some are worth reading, some aren't.