Hello there @ABTOMATO!
You are on the right path, setting a Custom Time Dilation for each actor in which you need to stop physics, should render the results you need.
If movement is not fully stopping, try to combine it with a blueprint change to the Global Time Dilation value. This value cannot be set to zero, but on its lowest value (0,0001), combined with your customs per actor, should do the trick.
Further methods for physics manipulation can be found here: