Wow, that is some good damage to the tree.  Does the crown/foliage look ok?  The pill bugs will be secondary critters that like moist environments and cover, as well as eating debris etc.  So they are not the cause of the issue I would guess.  but I don't know much about this tree and it's problems.  It looks like boring insects and decay in the picture.  I don't have a good recommendation for treatment, I would just watch the tree, and if the crown remains healthy hope that the tree can confine the damage.  Sorry to say that.