OK, I Think I know the problem. When you make a torus you should start on the cross section (back wall) and draw the upper 1/2 profile only & then go to the "extrusion torus" preset. The bottom line in your initial drawing would end-up as the center line in your part. It's a matter of changing your "distance to axis" thats somewhat confusing but you can always re-extrude it at a different setting or just drag those points where you want to. To make the rounded surface use the curved control points & use squared-off ones for staight edges (like the outside flat part that eets the ground). Its' really easy once you do a couple.