Allow me to respond as follows..
1 and 2 (similar questions lead to the same answer so i am combining them) I absolutely believe that the major reason the adam and eve account is held to as literal by christians as a whole is that without a fallen first man there is no ransom needed ergo no importance to jesus. Working backwards they must believe in a literal genesis account to have foundation for their faith.
3) good question. Be it christianity islam etc etc humans seem to have a need to explain the past and chart the future. We like happy lies. Religion tickles the human need for hope and gives easy to follow directions. Basic programing for our basic brains. Only my theory.
4) in cult foggy days i took everything paul wrote as unassailable truth, because i was told to... having reevaluated with a bit more rational mind i am unclear why any christian accepts anything that pompous asshat said. He contradicts jesus and himself often, he wraps himself in false piety at times at other times he braggs to such a degree that he makes me want to pull him from his grave and slap him. Again, only my opinion