Snapedom

Yes, to all your points. (And thank you very much for the point about plot reasons not standing in for character motivation, etc. This is something of a pet peeve of mine, but until now I thought it was just me.)

Also, not warning Severus about the Elder Wand was potentially hugely self-defeating in terms of Dumbledore's overall goals. Having decided (for whatever inexplicable reason) that he will only be satisfied if Snape - whom Harry, rationally speaking, is NOT likely to trust - is the one to pass on the message to Harry, he then does not even take basic precautions to enable Snape to *do* this as effectively as possible. Failing to let Snape know that Voldemort will likely decide to off him for the sake of the wand mastery only makes it more likely that Snape will, in fact, die, and thus not be able to pass on the message. It was pure luck (aka authorial contrivance) that he was able to pass it on at all - Dumbledore could not have predicted that Harry would be lurking in the tunnel right at the moment of Severus' murder. (And if he could have predicted that possibility, it would only make him morally worse, imho. Because then Severus' death at a certain time and place would be nothing other a further use for him, in exactly the same cold way in which Voldemort tries to make use of his death. Neither of them cares about Snape as a person, as shown by their actions towards him. At least Voldemort tries to compliment him first.)