From your questions on both the squat and the deadlift, it is obvious to me that your form is not quite right. The squat is seldom missed high in the movement where all that is left is basically quads. I think you may be shifting forward/raising your chest prematurely, taking your posterior chain out of the movement early.
And at your bodyweight 300 is a light deadlift to be stuck. This generally means you're pulling it off the floor wrong, with too vertical a back position. Both these things indicate to me that you have not read my book, and probably need to come to one of our BB weekend seminars. Or you could post a video, the cheaper way.