[Semper911]

What problem do you see with the angles?

I think the angles work. If he was falling somewhat parallel to the ground, or slightly on a feet-first angle, the spike on the fence could have entered through the back of the neck, and then stuck on the inner top of the skull.

If there was enough momentum, depending on his weight and the distance he fell, there could very well have been enough force to separate the skull at the neck. The neck and throat don't have much structure to speak of.

Weird things happen.

[Redcloak]

I think that you've pretty well guessed the mechanics involved. The wide shot shows the fence bowed from the force of the impact.

Yuck. :p