i wish i could help, but there are several details i dot understand... what are "the 2 points along the average normal", where exactly should they be, the start and end point of the line in your patch?
what do you understand as "the average normal of a set of points"? points do not have a normal. surfaces can have a normal and the vector between two points can be interpreted as a normal.
also "which result -> All angles sume = 360º" where are the angles that should add up to 360?