Hi Lorenzo,
Thanks a lot for the file. Really helpful, and dropbox 
, very much appreciated.
Have a look at the screen-capture, then the text below will be much easier to follow:
https://www.amazon.com/clouddrive/share/t9YAlLQ6UsPi6TyjZB5UhwHdUU64y4ndJGWdNEKAelU
The Xpresso Tag sets the Pose Morph into action. While in edit mode, it will not affect the sliders, but since you might test those (in animate mode), I would switch the Xpresso tag temporarily to off. (Enable: checked off)
Then go to the Pose Morph Tag, and select one pose, set the slider to 100%, and change the points of the receiving mesh in the way you want to have the expression.
Set the next one up in the same way, select the pose, set the slider to 100%, and change the mesh.
Then switch the Pose Morph Tag to Animate and explore the sider of each pose.
The Xpresso Tag can be set to enabled if you are okay with the results.
Press the play button. The motion capture should work now.
One point that must be clear, the Motion capture delivers only value, not the facial-expression. How that value is used is not determined. This is an artist’s call to get the expression in the way you want.
To say it extremely: If the motion capture creates a value based on “open the mouth”, the pose-morph based mesh could be set up to create a longer nose instead. Again, just to make the point. You have the absolute freedom to create here, the support of the many values the motion capture provides here no determination. So for a cartoonish animation, you can create acting expressions that no regular face could do.
To have the face split into left and right needs attention in the middle. The middle of the lip, as in the example, needs to have half influence from the right and half from the left. Both together will add to 100%. If there are four poses for that area, then it will be split even more.
Please note that the new mesh in the scene has some problems in the middle of the lip. Fix this before you put any work into the animation or poses.
All the best and stay healthy.
P.S.: let me know if you don’t want to have your file here
https://www.amazon.com/clouddrive/share/YCL70bkr72XpLPEsRChSpVlcVdEvFxMTbisUFOUKCJI
I have set up four of the many mouth poses.
Screenshot
https://www.amazon.com/clouddrive/share/nNOJiAwt9HQBe8ycPcUCGB1GWclE09wgcGMNknLEFxM
