Howard wouldn't know how much chloral hydrate would kill her...but KE would...That's why I think the phone from KE to Howard on the morning Anna died was "instructions". The "Director" needed "Directing".
About the Chloral Hydrate...Who else knew Anna was taking this besides KE and Howard? It WASN'T mentioned in the early autopsy. Who "cued" him?
Perper *said* it was Dr KE who told him about the CH.