you mixshader setup is wrong.what you now have is the top shader is mixed with 60% black and the lower shader is mixed with 40% black.
I am not sure about the reflection-transmission hair shader,anyways you can connect the transmission hair shader into the free shader slot in the upper mixshader,and delete the addshader and the lower mixshader.
(only one mixshader with the two hairshader into it)
then you could connect a fresnel input to the fac of the mixshader.
maybe some has more experience with this kind of hairsetups
for the iridescence colors you could try a thinfilm shader.but for a simple setup you can use a colorramp that is driven by a fresnel input.
similar to this setup for the colors