I'm fairly new to modeling and rigging in Maya; so my question is: in the image below how can I unbind the rigs head from the shoulder pivot? I've searched online for why this occurs and I can only guess that it's due to bad Joint placement?
It depends on the bind method. Go into the ANIMATION menu set and select SKIN > BIND SKIN [options box] - and tell me which bind method you have selected.
I can then tell you how to weight your skin! :D
By the way, your joint placement is fine.
I would also like to add as an alternative -
You could simply use HUMANiK. Google that and youll get lots of helpful resources. It requires you deleting your old skeleton/bones, though. In the end, it is simpler to work with which is why I wanted to make you known to HumanIk. It may be right up your alley! Good luck, friend! :D