Cage,

Quote - Can the extra ERC for the jaw and eyelids be deactivated and reactivated using poses?

Yes the way ERC for the jaw and eyelids is implemented is a royal pain in the backside. The problem as I see it, is that the rotations drive the morphs, so when you rotate the joint the morph must get expressed. IMHO, it should be the other way round, the morph should drive the rotation.

If it was done that way, there are two advantages. Applying the morph would retate the jaw, but you could rotate the jaw without expressing the morph, and thus make a correction. The other advantage is that it would be easy to add an ERC dial  to disable the slaving. Yet another advantage is that you could have multiple mouth open morphs that all drive the jaw.

I'll look into all this, and see what I can come up with. I had been meaning to do this anyway, just needed a push to get round to it.