Is there a way to keep my scoliosis from getting worse?

Braces in some cases. Scoliosis can be "treated" with medications, exercise, physical therapy, chiropractic treatment, and occasionally steroid injections to help relieve the symptoms of back pain and/or lower extremity pain. However these alternative treatments will not correct the spinal curvature. Bracing can help prevent worsening of scoliosis in certain cases but only surgery can correct the curve.
Depends. Depends somewhat on the size of the curve. In an adult, a rigid brace is not a good idea as it can cause stiffness and atrophy. You would want to be followed closely and aggressively treated for any development of scoliosis as that can really cause a curve to progress. Consider seeing a scoliosis expert to discuss the options in your specific case.
Yes if indicated. If you are still growing & curve has been determined to be at risk for worsening, bracing can help. Once curve has reached 50 degrees, it is indicated for surgery in most cases. If it is a moderate curve in middle age, avoiding bone density loss, obesity & smoking can help prevent progression as well as regular exercise with flexibility, core strengthening & cardiovascular workouts in general.