The DSTATS are actually edited through the tab that says "Development Stats". The Last Season stats are used primarily to determine the Most Improved Player award (comparing them to Current Season stats).
You can also edit the DSTATS through DB Commander (or any other DBF editor) by editing the stats fields at the end (far right) of the database, that are marked DFGATT, DFGMADE etc. But it's much easier with the Toolkit. You just had the wrong tab.
