Maybe try exporting the project as a master and play it back in QT and see which it is. Is FC finished rendering. Generally I find that full screen image wise is more accurate. Not sure about audio issues.
Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.