yes. the "flip it" that you often hear in this place is referring to the flipping of the stem (making it going negative)

73 is actually +/- 17 degree stem. as most headtubes make a 73 degree angle with the horizontal, a -17 degree from horizontal makes your stem parallel to the ground.

84 is actually +/- 6 degrees, which is what you have.

a zero degree stem is not gonna get you a stem parallel to the ground.

as for websites, here you go http://www.habcycles.com/fitting.html