I see a difference between faith in the authority of a text, a tradition, a person, or an organization and reasoning from one's own senses, research, experiences, and values. I see how the perceptions of either one can be shaped by ideology and culture, as you say, but it seems to me that faith involves the arbitrary imposition of a claim of certainty (sometimes in the absence of evidence), while reasoning involves constant reassessment of new evidence coming in and shifting provisional points of view. For a lot of people, the advantage of faith over reason seems to be that faith provides a sense of closure ("Well, that's settled"), while reason requires great attention to the daily flux of information. I can see that faith is more emotionally satisfying than reason because it produces calm, instead of agitation. What's your take on these definitions?
As you say, we are more in agreement than not, though from our individual standpoints. Powerful people and institutions have often "used" faith and reason to further their own interests--whether "to redeem the Holy Land from infidels" in the Middle Ages or "to civilize unenlightened savages" through empire-building in the Victorian era. This bad usage does not invalidate either faith or reason in itself.
You say that people of reason prop themselves up on faith more often than they admit--and perhaps that people of faith rely on reason more often than they're given credit for. I agree. The difference seems to be which one is relied on more--and which is used to rein in the other.
I think there might be a story element in Enlightenment reason, as well as in Christianity. Of course, Christianity provides more of a beginning, middle, and end, while reason is more open-ended and tentative. The reasonable part of the mind has to learn to exist in a constant state of suspense. There are notable exceptions. Kierkegaard situates faith in the existential moment so that the Christian has to choose and act without full comprehension of the story. And educational TV programs promise pat certainties--"Tonight, scientists provide the answer to the question of the universe's origin"--while enlightened scientists may prefer to say they have "an" answer, and a fairly tentative one, based on hypothesis.
I see the narrative of reason in argument--dialogue and conflict in perpetual suspense--thesis/antithesis/synthesis. Positions are taken, put to the test, and defended from attackers. In the process, the positions are qualified, and new positions come to supplant old positions. Facts are processed and interpreted. New facts arise or are discovered and have to be considered. "Open-mindedness" does not mean that positions are avoided, but that they are subject to revision, should new facts or better arguments warrant it.
My problem (perhaps my only problem) with the "faith" part of knowing is that it tends to tack on an arbitrary "Hollywood ending" to the reasoning process--and I include "faith in progress" and "faith in science" among the forms of faith. Kierkegaard, reacting against the Enlightenment, though undoubtedly influenced by it, has a more honest (I think) perception of what it's like to exist. We have to live in uncertainty, so we have to live with uncertainty.
In the Gospels, Jesus often states his ignorance of the future and his relative lack of concern with tradition. His faith is in God's provision ("the lilies of the field"). His example is to avoid settling--to live homeless in the world and to raise questions about the very things people think were settled long ago. "No man knows the hour" is a phrase that means more to me than that future events are in God's hands; it suggests the element of suspense in existence. "Now," "at hand," and "within you" focus his teachings to the present (uncertain) moment. It's fascinating to me that Jesus offered so little commentary on the scripture and based most of his ideas on what he was sensing and experiencing at a particular moment--what he could see with his own eyes--a sparrow, a widow and her mite, a fig tree. Even admitting that other biblical passages may contradict this perception, I find that this is the ("irreligious" and "irrational") concept of Jesus I still find interesting.