It is an interesting question indeed, but your approach leaves no doubt that you are already 100% SURE that Napoleon had stole, embezzelled (or any word you may choose) the money. However, what about objectivity in research? I agree with Kevin - unearthing all the dirt on Napoleon, while keeping it safe on Alexander, George, Frederick William, Ferdinand or any other of the royal bunch is not correct. I am not saying Napoleon was a saint, he had a plenty of wrongdoings, but lets keep a perspective on these things.
You also refer to Napoleon "allowing ALL his marshals and associates (Bourienne?)to loot and plunder as they wished" - However this is an overstatement and exaggeration. Even in case of Bourienne, that you mentioned, Napoleon took necessary measures when he was informed about it. Once again, I am not trying to justify him, but I also do not like when information is provided one-sided and only to smear his name.
Finally, going back to your question - "Back to the point: where did the money from the theft of the wool in Burgos go?" - Unless you or Oman have specific documents indicating Napoleon sneaked into the barn/house and "STOLE" the wool, there is NO basis for claiming it was a theft. It can be defined as requisition, I believe, which is quite different from theft.
With best wishes,
P.S. You mentioned it was a private property, but whose? whas this person involved in anti-French activity? Despite this, I would love hear what happened to the 15 millions anyways:)))