The results you get on the net price calculator does not guarantee that this is what you get nor does it imply a contract, for you to go back and ask the school why didn’t you get X.
Op stated she ran a few scenarios. However, did she run it with her D’s **actual ** numbers?
it seems that this scholarship is not solely based on grades and scores. Unfortunately you don’t know what the institutional mission is and how the school is going to use scholarship to woo students who they believe will fulfill the mission.
It looks like on face SMU does not have guaranteed merit.