To get a torus shape, you can just use the 2d shape editor, draw out the cross section and hit the revolve button.
The problem you have with your spirals is that the sloped sections are no longer planar polygons - you need to split each one into two triangles, since triangles are always planar. Non-planar polys are virtually guaranteed to cause nasty BSP issues. Splitting polys is not really possible in UED - they have to be there from the start. You could try making the spiral from a load of tesselated cubes (a cube with each face divided in to tris - you just select the 'tessellated' option from the cube dialog). You could vertex edit that into shape, and if you got it just right could probably duplicate the same shape and fit it together with the others to make a spiral. This isn't ideal tho.
To get spiral shapes, I find the best tool to use is tarquins extrude brush builder - you need to enter the cross section vertices numerically, and then define an extrude path in your case a spiral. You can work out the points you need with some basic math. You can get the brush builders from tarquins's link at the bottom of the forum front page.