Okay thank you that clarified everything. SO...

his left side wasn't targeted during the initial treatment. It was his right. Post treatment it jumped the midline and was found in the left side. Surgery was done. With the number of nodes involved on the left side he should have radiation (and possibly chemo) to the left side.
If the left side wasn't targeted in the initial treatment then its not that it didn't respond, its simply that it didn't get much or any of the rads. There is always a spray radius but that is usually far less than a targeted treatment. So this should be available to him now.

This is a recurrence. having had nodes pop up and salvage surgery on the other side to me is reason one to go through another round of rads, and then the number of nodes involved would also suggest to me that he should have it - even as a precautionary treatment.

PaulB has been through this before and has had numerous radiation treatments. He may be able advise you - but I would continue to push for follow up - multiple nodes tells me this is an aggressive cancer particularly because it jumped to the other side after surgery, radiation and chemo - go for another opinion if you have to. It may be that he has no cancer - but with his history, and age - i would push for the maximum treatment just to be on the safe side.

HUGS.