What is your pawn’s mass? I have tested this too and the AddForce() method seems to me to require the Acceleration (in cm/s/s), NOT force (in Newtons). Multiplying the AddForce() first parameter by mass makes by pawn go ridiculous speeds, assuming its Acceleration * Mass (which is Force in Newtons, times 100 for Unreal Units).
I have tested with different masses, using acceleration as the first param makes them all go down at the same speed, whereas using force as the first param (Accel * Mass) makes them go at much higher speeds than I expect.
If your mass is 1 kg in the example you illustrate, that would result in the expected behavior, but it seems based on my testing any other number results in unexpected behavior.