Separating curves and using them to split surface


I started by converting a mesh to a surface as they were tubular. Now I was able to extract the edges of the mesh as shown below,

I am having a hard time separating it into two closed curves. The idea was to use the smaller curve (marked by the color red) to split the surface and achieve surface ‘1’ as shown below.

I tried using the simple command “Surface Split” but then I get like 4 separate surfaces when I bake it. Is there a way around this?

I have attached the meshes and the code.

Thank You (47.1 KB)
Mesh_With _Hole.stl (158.5 KB)
Mesh_With_Fill.stl (358.5 KB)