And, can you please explain the “Actuator Control FFT” and “Angular Velocity FFT”, what it does and what it shows?
It shows you the frequency components of your angular velocity and actuator controls. You would look at the FFT to identify frequency bands to apply your notch filters. For blade pass frequency or frame resonances. I am not the best person to ask about this though, I have less practical experience than others.
I think I see now exactly the issue with yaw. Notice that 4 of your outputs are pinned to their near maximum values in an attempt to produce yaw torque. This is ineffective as you can see the heading changes very very slowly.
Multirotors produce yaw torque by using the angular momentum of their propellers. This is achieved by increasing the RPM of CW propellers and decreasing the RPM CCW propellers (for positive yaw). You are likely facing problems with the design of the vehicle due to the large mass moment of inertia of your airframe. Since your hover thrust is at 60% you already do not have much headroom for generating yaw torque. The propellers with increased RPM are hitting their maximum values and the propellers with decreased RPM are hitting the bottom limit of RPM before hover thrust is lost.