@slsl6
I have no experience shooting oil paintings, so I cant comment on that. What do you typically zoom to in order to take your images? What do you mean by, "look horrible"? Some example images might help determine what can be done to help you out.
I love macro lenses, they're some of the sharpest optics out there. They also have their limitations though. If you do not have the ability to zoom with your feet, the zoom lens you have might be better for your needs. Also, when you mount a 60mm lens on your D70s, the effective focal length would be 90mm. Great for getting close to shoot the details of the swirl marks made by the brush, not so great if you don't have the space to move back far enough to get what you want in the shot.
I might suggest a 35 f1.8 rather than the macro. This will give you a focal length combined with your crop sensor similar to what we see with our eyes and will allow you to shoot in lower light situations, (museums) due to the larger aperture.
You can also work with the camera and lens you have by using a tripod, slowing the shutter speed down to allow more light to the sensor and adjusting the aperture to f8 to get the sharpest image all while keeping the ISO as low as possible. for indoor low light shots, try 1 second, f8 ISO 200. If its too dark, slow the shutter more. You will want to use a shutter release cable or the camera's timer to eliminate the shake created by pressing the shutter release button and a stable tripod is essential for slow shutter speeds. Bonus points for using a speedlight with a diffuser but flash isn't always allowed.