You can use the Solidify modifier to make an object hollow:
The above screenshot is taken with a Clipping border in effect to show that the torus is hollow.
Also note that unless you need the ends of a curve to be filled or use, there is no need to use a bevel object. Since a torus does not have ends, using a bevel object is not necessary unless you want a non-circular profile.
There is nothing wrong with using a bevel object, as a matter of fact it gives you more control. I thought I'd point this out because it does not seem to be necessary in your case.
To make a torus from a curve circle object without using a bevel object:
Set the Fill in Curve > Shape to Full
Set the Depth in Curve > Geometry > Bevel to the overall thickness of the curve.
Set the Resolution in Curve > Geometry > Bevel to the the number of minor subdivisions you want.
If you then add the solidify modifier, you will have a hollow torus like in the first screenshot.
- You can adjust the thickness with the Thickness setting the the Solidify modifier.
- You can adjust the minor radius with the Bevel depth, or AltS in edit mode.
- You can adjust the major radius by scaling the curve (S)