Hi timely,
Oh, how I wish I had the ultimate exercise program to recommend! (Sigh....) All I can do at this point is share what may be helpful.
Like you, dealing with the joys of osteoarthritis and osteoporosis, with scoliosis being the cherry on top! After "ignoring" my scoliosis since being diagnosed in my early twenties with idiopathic adolescent scoliosis, too late I discovered the scoliosis has not been ignoring me. It has gone from mild to moderate, and now complicated by sarcopenia. The OP has been hand-in-glove with the muscle wasting.
I've been working with a PT who specializes in the Schroth method for treating scoliosis. Since making her aware of my OP diagnosis, she has made helpful modifications to my scoliosis exercises, adding some hand weights to my regimen. I strongly suggest that you work with such a specialist, because as you know, scoliosis involves a 3D rotational disfigurement, and each case is somewhat different. I have dextro thoracolumbar scoliosis and must use a supportive towel roll for some of the floor exercises. It would be great if there were a video series that addressed the unique needs of those diagnosed with both scoliosis and OP.
Because scoliosis sufferers are at increased risk for sarcopenia, I have added 5 mg of creatine to my daily supplement intake. (If our muscles can't support our frame, then that puts added stress on our already weak bones!) I use my Marodyne LIV machine twice each day to promote my bone density and muscle mass. And so many other daily interventions...