First of all, REMAIN CALM! I cannot emphasize this enough.
I experienced something very similar when I applied to med school. It seems that I somehow managed to get accepted, on the first try no less, despite having an abysmal application.
What worked for me was acting like an absolute studmuffin.
You are a badass. Your application may not look so good, but it obviously can't be trusted. I mean, look at you, look how badass you are! *strut*
At the interview, acknowledge any imperfections, but brush them off as being in the past and not representative of your current and future level of studliness. Then they will bow before you and rank you highly.
Go Jeff, go! You stud you!