I know I have a deviated septum
but no sure if it could cause all that. I find myself having to breath more through my mouth than my nose. It is easier for me.
I have tried some breathing exercises that help somewhat. There is a website from someone named Michael White where he sells a CD to help with breathing exercises. It does seem to help somewhat. It shows the importance of breathing and how to do it properly.
I also tried your exercise HAVA and it seemed to help also.