[Baalz]

1) All friendly units including commanders. As far as I know nothing "in battle" is contingent on which commander troops are assigned to (other than "guard commander" I suppose)

2) Correct, I think the game probably counts them as their original type rather than an undead mummy.

3) No idea, impossible to test but units with a lot of afflictions don't seem to stop getting new ones so I'd guess b.

4) Yes, all units. If your armor is destroyed by ie. "Destruction" however it will be repaired at a rate determined by the unused resources in the province you're in.