How is $\Omega_0 = 1$ when the characteristic "teardrop" past light cone seems to admit curvature? Introduction:
The top graphic is just one I pulled from a page describing the process of detecting cosmic curvature. The second graphic is one I drew up to illustrate my misunderstanding.
My assumptions are these:
1) The characteristic "teardrop" past light cone is a correct representation of our observations.
2) Curvature is measured by the angle between two converging photons.
3) WMAP measurements of  $\Omega_0 = 1 $ are correct and accurate.
Question:
1) How is it conceivable that  $\Omega_0 = 1$ from WMAP measurements if the teardrop past light cone admits initially parallel yet eventually converging photons?
It seems as if $\Omega_0 > 1$.
2) Photons live on the surface of light cones or teardrops and there is clearly some degree of curvature in the early universe as displayed by the graphic. If $\Omega_0 = 1$ then what exactly is meant by curvature if the curvature in the bottom graphic does not contribute to $\Omega_0$.
Keep in mind that the bottom graphic shows two dimensions of space and one of time. 
I have done my reading on FWR metrics to a reasonable extent and I am still lost with this so could one of you fine PSE users please show me specifically what I am misunderstanding and provide context, math or intuition. 
Thanks in advance friends.
 
 A: The "teardrop" shape is perfectly compatible with a flat universe. Remember that even though the trajectory looks curved in the x/t-plot, the photons travelling along the lightcone are only moving in the x-direction. 
Think of a photon sent out towards us from some distance right after the big bang. At first even though the photon is moving towards us, the space in between us and the photon is expanding faster than the speed of light so the distance to the photon actually increases. However, as the expansion of the universe slows down, eventually the photon catches up with the expansion of space and reaches us. 
I think some of your confusion stems from the fact that it looks like the photon is directed away from us at first, and then somehow changes direction and eventually reaches us. This is a mistake! The photon is always directed towards us, it is just the rapid expansion of space right after the big bang that makes the distance to the photon increase faster than it can approach us. 
