On the bit means that the horse is using himself, stretching his back, lifting it, and rounding his neck. The vertical refers to where his head is, it is vertical to the ground. From these pictures I don't think your horse is either.
Here is a horse that is on the bit, and on the vertical: http://cache.eb.com/eb/image?id=1302&rendTypeId=4
Your first pic:
His head is just there - he's not using himself, and there is no contact for him to stretch into.
He could be using his hind end more, push him forward and get him to step under himself more; his head is behind the vertical, means he is avoiding work.
His legs are still trailing behind him, and his head is just in his natural position.
Fourth Pic: behind again, and not using himself.
Five: he looks like he might be behind again
And 6 is just cute
What you need to do is get him moving off his hind end; think of riding him forward and up (I tend to say this with the beat of the gate- it helps me). Don't worry about where his head is, as he gets stronger his head will naturally go where it needs to.
Good luck, hope this helps!