When requesting divine help is it in general best to ask for the moon, or would the divine realm sometimes stand down if given an impossible task?

Strictly speaking, we always stand down when given the impossible but we see through the wording of your question. What you truly want to know is, "If you are overreaching compared to what is possible, does that mean we will do nothing because we cannot match your request precisely, as it is certainly the case we must follow the human lead?" But if you think about healing work in general, it is almost always the case people are asking for more than can be delivered, at least quickly, so we are always in the position of making an approximation, making at least a start, getting the ball rolling, so to speak, even when many times there is no perceptible beneficial outcome for the client and it is as though nothing was done of any value when, in fact, effective healing is underway because it was launched in the highest and best way and is capable of resolving the problem eventually. So you need not over-worry about asking for too much. Only asking for a specific outcome, and that alone, and so defining it that nothing else need be included, will result in a misstep where you might end up with nothing because you have not defined adequately a range of possibilities, up to and including what could be impossible and seems daunting to you. So we would always recommend seeking the highest and best outcome whenever you reach out to us because that creates a high-level intention, if nothing else, and to the extent it can be honored may well provide the requisite fuel for the work to be done to a state of completion, even if that takes a considerable period of time to bring about.