I think you could rotate the body more for the arm to get body out to the side more. Now i think you are more lowering the body and go back with the arm itself. Coult at least stop more with body if you turned it up a bit more, now no time to stop the body. Then relax the arm and have racket head a bit more pointed down. By getting arm more relaxed and turning up body/more earlier you can get more motion in the arm. Need to get more natural flow and less stiff.I am not sure if I understood what you mean.
Right now I do seem to struggle vs empty slow shorter close to the table balls because if I try to accelerate it goes out even though it has arc and curves down. But because of the incoming sidespin (if they serve pure sidespin) I am scared to brush it too slow. And even if it would land on the table its either too short or too slow and I am not getting the initiative that I want.
I see franziska using his legs like me rotating into the table on half long balls with a lot of speed. But my balls tend to go out more. With my technique that is more upwards naturally I am not so scared of the net really.
And even here vs block my followthrough motion stops very close to my head armpit wide open and lifted too much up imo. It should end more in front of my head I think armpit not lifted so much that the angle is above or 90°
I think on half long ball you could either step in and kill it if it high and then you need some body if you have time. At half long ball that is low i think forearm is more important. As long as you brush with forearm you will get spin. I think having a open racket angle or looping upward are limiting in the long run. If you then can hit the ball fast it will just be high and go out. Better to try to close and go a bit more forward.