It is great your financial situation is better than you thought! I would strongly encourage you to use some of that to explore other PT ideas. Even if you just met with the PT a handful of times they could give him ideas get the most of his home exercise. It could save him a lot of time and pain. With the scoliosis and hypotonia it maybe tricky to find exactly the right sorts of exercises that are appropriately challenging and don't at the same time risk him getting hurt. It may be that someone else could find some easy solutions that would result in bigger improvements faster.
As far as heating pads - have you tried one of these?
http://www.amazon.com/Moist-Heating-Pads-TheraTherm-Rectangular/dp/B0006NMT5U/ref=pd_sim_hpc_2 They are great. A totally, totally different thing than the sort of heating pad you get at the drug store.
