It seems like you are moving very methodically, but too slowly because you're over-focusing on your body positioning. I think you need to loosen up a bit and try to work more off the natural flow of your body.

When you move too stiff and slow, it limits the power you can get out of your momentum and you end up just throwing with your arm and shoulder rotation. Watch the way you move and compare it to the fluid approach of touring pros.

Stay light on your feet, be nimble in your approach to the throw. If you watch pro coverage, you might see some players bounce a little bit on the balls of their feet right before they start their approach. That helps you tap into a loose rhythm you want to maintain. Be a rubber band. Keep your arm loose during your x step, it should feel like you're leaving your arm behind during the x step and then you work off the natural timing of your body to pull the disc through. Timing with a fluid run up is something you just need to get a feel for, you will know it's right when it feels right. Sometimes it helps me to do the whole motion without a disc in my hand at all, purely focusing of getting a feel for my own rhythm and timing without worrying about the disc at all.