Regarding # 1: I think LE photographs would suffice. No need to remove that portion of drywall. What evidence can you obtain from empty space (i.e; hole)
Regarding #3: Same as above.
That leaves me looking at #2, and I can't see any earthly way that cancer/poison/neglect would cause bodily fluids to be on a wall.
JMO
If Zahra was killed by being slammed against the wall, I should think it would be possible that LE would remove the drywall for testing, *after* the photos. Maybe not the whole thing, but I could see where WenWe is coming from, I think.
ETA: And I apologize for not knowing this (modding gives me little chance to really consider the cases themselves, sadly), but are we certain LE removed that section of the wall? Perhaps someone else did, before, in order to cover evidence of the above? (Just a thought.)