Need more throws to see better.
1. The first thing i noticed is that your strides are very long. Keep your strides shorter: it takes less energy and it allows for smoother, and better torque.
You dont see a baseball player with his batting stance really wide for that exact reason.
Its all about learning to be athletic in your movement.
2. Dont be so hurky jerky, keep it smooth. This saves energy and allows for better control and distance.
Dont reach try to reach back, let your body's momentum move forward while your disc stays in the same place.
-Move your arm slow to fast
EXPLANATION: let your bodys rotation and momentum pull your arm and disc until it gets to the center of your chest. Once it reaches that point, use your arms to pull it and whip it out of your hand.
3. Finally, keep every part of your body close to your torso. Just like baseball, keep your hands inside your body. Dont let the disc and your arm do a circle when throwing a disc. It should be a straight line from behind you [reachback] to infront of you [release].
Try fixing these one at a time, dont overwhelm yourself. Hope this helps!