Extremely sparse volumes, such as yours, are not well suited for 3D reconstruction or analysis. You cannot utilize high in-plane resolution if your slices are so far apart, as there is no information about how to fill the huge 4mm gaps between the slices.
To make the volume less sparse, you can crop volume with “Isotropic spacing” enabled (and increase “Spacing scale” if the volume is getting too big). You may try to further reduce staircase artifact by using Smoothing effect.