I didn't read all of this, but I will chip in a couple of comments.
1. The Gospels were written by four different individuals. Regardless, if the Bible is the inerrant word of God, there should be no discrepancies, but they exist.
2. I didn't consult the Greek (yes, I've studied it). If in fact the tense in Matthew is the aorist, then it merely applies to an event in the path. He points out some scholars insist it should be understood in the past perfect. No, it should not. The past perfect implies a COMPLETED TASK IN THE PAST.
Think of it this way: "I went to the store" vs "I have gone to the store." The first merely states I went to the store, and while it may be taken as having made it to the store, it doesn't actually say this. In other words, "I went to the store, but was met a friend and talked." So we don't know for certain that the store was actually visited without further information.
On the other side, "I have gone to the store" implies that, yes, I actually made it to the store.
Keeping this in mind, nothing in the aorist says that the stone was already rolled back, and most likely was not.