If this is aCML, it has been discovered very early. I use the word "if" because aCML is difficult to diagnose and usually includes much higher WBC than you have shown, and high blast count (yours is zero). So although I do not have all the information, it would seem difficult to properly diagnose this as aCML at this point. I would hold onto a bit of scepticism about this until more testing is done.
The JAK2 mutation test is a separate test. You should ask the MDA folks if it has been done, and if they will do one.
From what you have said, your marrow cellularity is high (granulocytes and megakaryocytes -- which are pre-platelet cells), your spleen is enlarged, and your monocyte count is high. The back pain is odd, and does not seem to be associated with aCML unless it is the spleen, which I doubt.
With such symptoms and normal WBC, diagnosis is not easy. It could even be very early stage regular CML that has not progressed enough yet to diagnose. Or there are other possibilities. My purpose is not to try to diagnose you, but simply to point out that I have a difficult time understanding why the docs would jump straight to a diagnosis of aCML at this point. There is not a specific cytogenetic marker for aCML that would make a diagnosis easy to confirm (Scuba's question), and it is usually diagnosed by a lack of any other explanation. Such a diagnosis does not seem possible at this point, and although it could be a lucky guess, you would prefer a better approach.
If you have other high or low counts or symptoms, they might provide more pieces to the puzzle.