1) What I seen done is either a forward caretaker to both repair damaged units in that area and to reclaim whatever dies in it's range, though sending a cheap constructor or two and ordering them to reclaim in an area works well enough
2) I don't think there's a setting for specifically that, but pretty sure there is one to not allow a commander to be selected by dragging the selection box to get several units at once, I don't remember where and what exacly that setting is though
3) It's important to have storage if you expect a burst of metal gained (from reclaiming for example) and aren't fully using your metal, however if you use more metal then you gain you can get away with not building any storage pretty much, the important thing from a commander is it being a constructor that can be customized to be a bulky combat unit or whatever else you want as well as very minimal (but still existant) metal and energy generation