How to draw a isometric spline from a discontinuous solid contour?

Hi,

As shown in the figure below, the contour of the leaf-shaped solid part is not continuous. It is inconvenient to use "Convert entity references" and "Offset Entities" to directly generate a closed curve closed loop.

My current method is :

To draw spline curves directly, but it is difficult to make them equidistant from the solid contour (It means the curvature is the same, the spacing is the same). Do you have a good way?

SolidworksModeling And Assemblies