How to avoid Mesh Distortion when Curves cutting themselves, especially with Subsurface Modifier? I am failing on a embarrassing challenge. I am trying to create an actually pretty simple form, but I cant finish my work without distortion on my mesh.



This is the object I am working on.

So far I tried different strategies, but I have always the same issue:



As you can see, the Boolean modifier and all my other attempts failed.

The problem is the overlapping mesh obviously, but I don't know how to fix it.
My best attempt so far was to make the whole object from only 1 curve:



But then my Circle looks a not really symmetrically. And if you look closely enough you can still see a little shadow/distortion on the point where the curve hits herself. 

Is there a common known workflow or something to help me finishing my project?
As you're talking about booleans it looks like you're open to do it with mesh (rather than only curve), so here is a solution:


Create a torus (Major Segments: 24/Minor Segments: 8).
Duplicate one of its circle, make it another object, extrude on the Z axis.
Boolean the 2 objects.
In Top Ortho view cut in half with the knife, then mirror the whole object.
Use the knife to add some topology: K to activate, Z to cut through, C to cut orthogonally.
Give your object a Subsurf and Shade Smooth to test the result.
Use the same technic and also the Spin tool for the top of the object.