One of the many things I noticed is that your throwing arm is up way too early. You have to keep that arm down until you have built some torque with the hips and are planting that front leg.
Your high leg kick may help you gain speed down the hill once your body starts to come forward, but any momentum you are storing is being nullified when you collapse your back knee during the stride. Your body is moving down (almost a sitting posture) when it should be moving forward.
Right now, your lower body is working hard to catch up with your arm position when it's your arm that should be trying to catch your lower body.
By the time you are in a good throwing position, you have nothing in the tank and you are throwing darts.
Notice also how, at release, your center mass is very low and behind your lead leg instead of being up and over the lead leg. Your lower half is applying the brakes before you even release the ball.
Overall, the delivery you have developed looks very uncoordinated and stiff. In my opinion, this will take a while to correct all of this and any plans you have to walk-on anywhere in the short term should probably be re-evaluated.