When you are dealing with mole calculations, whatever you do to one side of the equation you must also do to the other. .5Fe is 1/8th of 4Fe, so in order to determine what it will yield you must divide the given amount of Fe2O3 and divide THAT by 1/8th, leaving you with .25 mol of Fe2O3.
57.0 is it rounded to three sig figs. You count three spaces then round from there, which would be the zero and you would round down because the four is there.
