I have the same thoughts on George Mason as you. My advisor was really pushing me to just apply for the PhD anyway but I was too intimidated so I am going for their Masters, along with a couple of other Masters programs and some PhDs. Your GRE is much higher than mine, similar GPA, and similar research (although I do not have publications, and do have a couple years of lab experience). If you really want to apply for the PhD, you might as well. I think you have a chance. I am almost regretting not going for it myself, although I keep telling myself it is a safer decision to go for their MA.