Wow – i would change your embouchure. If you are biting that hard, that will tense up your air flow and make it harder to keep a steady pitch.
Try to start with a double embouchure ie top lip curled under top teeth, bottom lip curled over bottom teeth. Place mouthpiece on bottom lip and then lower upper lip onto top of mouthpiece – then push the top lip out of the way with the top teeth coming down and resting on the mouthpiece.
This results in a flat even tensed horizontal bottom lip which will give a firm steady pitch, then with the top teeth resting on the mouthpiece, seal off the mouthpiece with the rest of the top lip. Your embouchure lips have should now have a firm seal around the mouthpiece – start blowing, and gently increase the pressure by pushing the bottom lip up.
This is where you fill your stomach with a decent amount of air, and pull your stomach in firmly to increase the air pressure on the mouthpiece, so the stomach pressure is more in use, rather than using a lot of air pressure in your mouth. The more air pressure you use in your mouth may result in you biting more to control a steady pitch, whereas you can take a lot of pressure off the mouth, if you use your stomach to control the pressure instead.
this probably wont help, but it’s worth a try.
