I had a left neck dissection with 56 nodes removed. It leaves the tissue more rigid because you have effectively removed the drainage system from the area.
That is referred to as lymphedema. Various massage techniques can assist in reducing it, but it will never go away completely. activity, fatigue, etc. all make mine swell a little more than normal. It was also a lot more pronounced when I was still lying in bed a lot.

That said, I have the comfort of knowing that all nodes were microscopically examined and found cancer free, which is important to my state of mind

If memory serves, your Dad had radiation too, didn't he? That will also cause rigidity in the muscles. The radiation does effectively "cook" the tissue, making it more like a grilled steak and rigid to the touch.

The massage that I've had done on my face and neck for lymphedema is pleasant enough, but really hasn't changed anything. What the therapist tries to do is to massage the area starting high on my face and always working down, to force the accumulated fluid lower into the upper chest where the lymph nodes are still present to drain it away.

Some people have had really good luck with it, some not. I know that it is specialized training for the therapist, and not that many are qualified to do it
Best,
Wayne