Would the insurance pay for PT or for therapy with a psychologist? Often insurance is less likely to cover OT than they are PT. We found PT more helpful than OT for hypotonia. Really with a kid as old as your son, once you get set up on a plan he may be able to accomplish as much at home with regular exercises as he could in therapy anyway. Another idea might be to look around a bit in the homeschooling community for an athletic high school age kid who might like to teach swimming or work on some other physical activities too. That may be inexpensive and highly motivating too.
My sympathies on the possible scoliosis cast. I wouldn't underestimate the possibility of a kid rising to a challenge or getting out the other side a stronger person. I know the situation is not what you'd choose but he may surprise you by handling it better than you expect especially because he's a smart kid and he is old enough to understand the whys if he needs the cast. That can go a long to helping with the rest.
