Forgive me for not reading your whole post as it is quite long, but going of the symptoms that sounds alot like me as a kid Deep breaths when it's bad, opening your mouth wider when talking, try talking slower (sounds obvious but it helps), and also stretching your tongue by touching the top of your inside mouth and then opening the mouth wide vertically are some exercises i can remember and they all definitely helped me, if you can afford a qualified speech therapist then do it, if not you can try find some exercises online like YouTube I wish you all the best man