Take for instance the existence precedes essence aspect.... did Adam exist in essence prior to his physical creation?
We know that Jesus existed prior to His incarnation but is that true for us also like David suggests in the psalms?
I assume that you're thinking of Psalm 139:15-16. Jeremiah 1:4-5 might also be one to consider in the possibility of man's existence prior to being physically born. But neither of these passages are definitive statements of such and they actually point much more to God's omniscience. Nothing in the Bible explicitly states this notion of existence preceding essence in mankind.
Also, this is really an issue of doctrine and not a matter of existential philosophy in the sense of "leap of faith."
Religious existentialism has removed the intellect from faith and made it a matter of passion, only relationship and action matter, even if those passions are misplaced. So you have men like Rob Bell who insist that Christians should live a life of faith regardless of its historical accuracy, this is a terrible leap, it leads to Christianity being thought of as the best way but not the only way. It brings man to hopelessness in the matter of knowing God.
Here is something from Francis Schaeffer on the matter of existential thought and its beginnings with Kierkegaard;
"This[modern existential thought] turns upon his writing of Abraham and the "sacrifice" of Isaac. Kierkegaard said this was an act of faith with nothing rational to base it upon or to which to relate it. Out of this came the modern concept of a "leap of faith" and total separation of the rational and faith.
In this thinking concerning Abraham, Kierkegaard had not read the Bible carefully enough. Before Abraham was asked to move toward the sacrifice of Isaac(which of course God did not allow to be consummated), he had much propositional revelation from God, he had seen God, God had fulfilled promises to him. In short, God's words at this time were in the context of Abraham's strong reason for knowing that God both existed and was totally trustworthy. This does not minimize Abraham's faith shown in the march to Mt. Moriah and all the rest, but it certainly was not a "leap of faith" separated from rationality."
In Christ,