Here's something Bob C told me that I keep safe:
Your chor action comes after the dialog action, and is set for replace.
In the chor action are some of the same bones which control the face,
including a null called synch...
If you need to animate these face bones in the chor too, then you can
solve this problem in one of 3 ways:
1) You can animate them in a chor action which has the blend method set to
add instead of replace.
2) You can animate them in a chor action which is above the dialog action
in the tree, so the dialog will override the chor action.
3) Place the motion in a chor action whose duration expires just before
the dialog becomes active. If you need motion after as well, you can
create yet another chor action.
Not sure about cd 2.