Since all you want is a simple FK spine, you can just delete the Torso Translator and Head Translator, use the "Attach Bone" button to attach the head bone to the Torso bone and the Torso bone to the Lower Spine bone, and set the "Lock IK" property for the Head, and Torso bones (in the Model Properties) to ON. That should give you what you want.
You don't really have to mess with adding an extra layer of control bones for the spine unless you just want to.
There is only one relationship in the spine. It is in the Bones model > Show Lower Spine Relationships. The Lower Spine has a constraint to roll 50% like the Lower Hips bone and 50% like the Torso. As long as you are aware of that, you should be able to add whatever control structure you want to the spine without interfering with the existing constraints.
I didn't use any expressions in the rig, so you don't have to worry about those.