I mentioned rounding as a problem earlier on purpose so checking out the Climo bit from Clearwater Disc Golf Store should help. You should test the differences with your current leg muscle tension vs tensioning up so much that your knee angles are halved to almost straight. Basically you want to be more upright. You don't use any hip area muscles in the throw. You need to twist the hips so that the upper torso turns to the right before the disc leaves. You don't reach back nearly enough and lose a lot of distance there. What you wanna do is to see how long your body control works now adding more reach back by turning the heels at the target and moving the disc as far away from the target as possible. Chances are that your balance, confidence, automated movements and snap plus all the associated timing differences will leave your shots shorter at first. Just stay upright and maintaining angles and moving in correct sequences taxes the brain so that you forget to accelerate the arm. Shortening the reach back in steps tells where your current optimum is. It can take months to develop the longest possible reach back but man you'll be glad when you manage that with good snap in the end
These are all pretty standard new player things and there's plenty to hone so another video would be great once you feel you've worked in those changes. One can't change too many things at once or you'll throw like crap. It takes time to automate motions and only a lot of field practice shortens the learning curve. You need repetitions, repetitions and repetitions. Everyone goes through that unless they've gotten great body control from previous sporting background.
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.