Since when are not UNC and NC State in the top 10?? I have been admitted into one of them and I had only SLIGHTLY higher GRE scores, so I think they are fine. There is no consensus or right/wrong in terms of GRE scores, as long as you have other things to show for yourself, like good major GPA in your case. But yeah I'm sure if you can retake it and get a significantly higher score, go for it!
Idk about Pittsburgh, but UNC and NC State clearly state on their websites that intro stats/ probability courses are prerequisites for PhD. So I think without these, it will be hard/impossible to get in. Clear question that will arise is: Why are you applying for stats when you never took a single stats course?
Furthermore, isn't it a bit late to be applying for Fall of 2015? The deadlines already passed for most schools...... Maybe you could get the prerequisite courses (stats and prob, ideally beyond the intro level) and try next year?
