[question about what and why it's locking wrong from x43 on]
It's all moving together and with even timing, but it's good that you "see" that something is off. :)
Try this, scrub back and forth through the scene from x20 to 32 and you'll see how the body parts are moving separately, but when you scrub from x45 to 60, it looks like you just animated the root so that the whole upper body rotates up and back.
You will have to offset the chest and the head more. The head could look towards us. He could change his arm pose so that the chest rotates towards as well (less than the head). The head/chest/body movements also have to start and end at different times, to make it feel more organic.
One last thing, speaking of scrubbing from 20 to 32. If you look at the root, it's moving pretty horizontally from left to right:
Everything needs to move on an arc (even if the arc is very small). Now think about what the legs are doing to the hips and root.
Root is high because SL leg is straight up, pushing root up. As he transitions from left to right, the root will dip, but when he's on the right side, the SR leg will push the hip and therefore the root up again. My green curve is exaggerated, but that's the idea. And if it means straightening the SR leg a bit more at x29, then that's okay.
Hope that makes sense! :)