I am not sure if this will help, but I have a lot of sciatic pain as well & have been going to different chiropractors to see what will help me. Stretching the hamstrings on the effected side slowly until it pulls, hold it for a couple of minutes and then relax. Best thing that helped me is lying on the floor on my back with my husband stretching the hamstring/leg upwards. I am not very good at being regular at excercising, but I try to keep up with it. I think just in general stretching the lower back/hamstring helps relieve my pain.
Also, maybe try an accupucturist. I haven't gone to one yet, but planning on going soon.
I hope he finds some relieve soon! I understand his pain.