No advice, just wanted to say that I am sorry you have another symptom to deal with on top of everything else. I hope that things improve soon.
I have the cement feeling in both my lower legs more often than not. It is amazing to me that they can feel like that and still work at all, as you said of your thumb. I am sure it is a PN symptom.
The "dead arm" feeling was terrifying to me the first few times it happened. Now I more or less expect it several times a week.