This is such a mind blowing performance! Mark, you did amazing and your tone stability is off the charts. You're so careful with your articulations and dynamic phrasing. It truly amazes me.
Try buzzing on your mouthpiece while keeping your cheeks in. Work on slurring up (on your mouthpiece) by using your corners and by making your aperture slightly smaller (instead of getting the velocity of air you need by puffing your cheeks). You can also try raising your tongue as if you were saying the vowel sound "eee" to increase your air velocity. Also keep the corners of your mouth in, instead of smiling. If you play with an upstream embouchure with 2/3 of the mouthpiece on your lower lip (like me), it might be a little harder to do, but it is still very possible. However, if you play downstream (2/3 of the mouthpiece on your upper lip), it should only take a little practice to keep your corners in. These are just suggestions, hope this is a help!
