Your final step length is ok for so slow run ups so don't change that yet. More speed allows and needs a longer stride. Looking from behind the tee to the basket you should move the right leg 6-8" right for making flat releases easier. Relative to first video from the side in the final throw.
That chest pause is a timing issue plus proper body placement and order of things happening issue. All you need is to move the disc from your left side to the disc having just passed the right pec maintaining knee, hip, torso and shoulders in 90 degree angle to the target. The really firing up the kinetic chain from the legs up. It should take just a fraction of a second of fluid passing over of kinetic energy from legs up to the fingers. Just like the inrush current of water into a water hose will snake it around initially seeing the first drops of water moving in the pipe coiling/uncoiling the hose. The body should move in a similar unrestricted smooth motion in the order legs pushing while pivoting, knees twisting in the pivot, hip explosion, shoulder turn right after the rear of the disc has passed the right pec immediately followed by elbow chop with killer acceleration from the arm, the wrist shooting forward and straightening from the acceleration induced bend straight, wrist stopping abruptly followed by the disc pivoting between the index and the thumb pinching hard.
That's a brief introduction to snap.
Flat shots need running on the center line of the tee and planting each step on the center line. Anhyzer needs running from rear right to front left with the plant step hitting the ground to the left of the line you're running on. Hyzer is the mirror of that.