Of Sticks and Stones

A few weeks ago, when my children were explaining to me how the reason that Aharon had to perform the first three Makos is because Moshe needed to display הכרת הטוב to the Nile and ground, both of which saved his life; the Nile as a floating baby, and the earth when he buried the Egyptian whom he had killed (there is an interesting lesson here as well: If the entire debt of gratitude to the earth was for helping him hide the evidence of his crime, and the crime was publicized anyway, we see that our requirement of הכרת הטוב is not contingent on whether the good deed done to us was successful).  It got me thinking about another similar episode.  We know that ultimately, Moshe is punished for hitting the rock in פרשת חקת, and the מפרשים all come up with different explanations as to what exactly his sin was (I have a more serious theory on that, but we'll save for another day).
Maybe, it seemed, an element of his mistake is the fact that a stone too once saved his life.  Remember that when Moshe was going back to מצרים after the episode at the burning bush, he was attacked at a motel by Hashem and was only saved from death when ציפורה took a sharp stone, and circumcised their son.  Perhaps then, he also needed to express gratitude to the stone, and hitting it was inappropriate.
The problem with all of this is in this week's פרשה where following the פרשת המן (magic food, not Purim ), in response to the Jews persistent complaints for water, Moshe cries to Hashem "מה אעשה לעם הזה, עוד מעט וסקלני" - What should I do for this nation, a bit more and they will stone me.  Hashem tells Moshe to take the זקנים and "ומטך אשר הכית בו את היאר" - the staff with which you hit the Nile.  And the He tells him to take that מטה, and hit the rock.  It is obviously difficult to say that Moshe was wrong to hit the rock in חקת, if Hashem told him to do it here in בשלח.  More striking, In שמות, and בשלח, it uses the word צור (or צר) for rock, whereas in חקת, it uses סלע - so the language ties the episode where the stone saved Moshe to the one where Hashem explicitly commands him to hit the stone, and separates the one where he is punished for hitting it without permission!  Finally, it seems odd that Hashem refers to the מטה as the one you used to hit the Nile, when as we know, Moshe never hit the Nile.  The Ramban notices this, and says that it means that Moshe hit the Nile indirectly - by telling Aharon to hit it.  There seems to be something here, but I can't put my finger on it.  If anyone has any insights, generally about trying to put these pieces together or specifically about the difference between the צור and the סלע, please let me know.

Hope everyone is having a great vacation.