It seems like bad form to have miles adjusted without even a brief comment, hopefully you will get your answers. It could be that the problem originated on the KLM side and DL is just rectifying what they no-customer-interface guys treat as a simple transaction. (I don't know details, but I assume Skyteam partners charge each other in some way for paid/redeemed miles.)

As far as reconciling activity, the Skymiles > My Skymiles > Account Activity page on the Delta website used to allow for exporting activity. Now there is a transaction-by-transaction summary in almost excruciating detail, sorted by date for each MQD and RDM event. There are entries for each segment of an itinerary and separate MQD entries for each transaction on Delta AMEX (not linked to a specific purchase unfortunately.) Rebooked award travel appears as a credit/debit, so it can get confusing.

Detail in and of itself isn't problematic, but it would be nice if there was a way to export for record keeping. If there is a way to export this info into CSV or some other format, I haven't found it.