Can't say if the jacuzzi will help. For Morgan's PT they had an underwater treadmill for the hydrotherapy the doc mentioned. We asked about doing this at home in the pool and were told it wouldn't hurt, but dogs mostly swim with their front legs so it might not help that much. We were also instructed to periodically pinch the webbing between his toes until he pulled his leg away to stimulate the nerves.
When he was going to PT they gave us a list of things we could work on at home but the toe pinch is the only one I remember offhand. Do you have an animal physical therapy clinic in your area? If so it might be worth asking them if they have experience with IVDD dogs.