I’ve been experimenting with breathing while holding a piece of gum or hard candy balanced on the tongue and not touching the palate. These cannot be backswing breaths due to the risk of aspiration, but rather just slow inhalation and exhalation to get the feeling of openness. Take out the candy/gum for a backswing breath for safety. Like you, I struggle with constricting the oral cavity which obstructs the airflow. Other ideas?