Wall is completely lacking in footwork and will never become a 4.5.
Seriously, you have the physical and mental energy to do this in an intense way, and that is really fantastic. I would just get bored.
One thing I would like to know is how much topspin you are putting on the ball. I find that when I put a lot of spin, the ball will not come back the way it is coming back to you. It will "reflect" sideways a lot more and dip down and die earlier after the bounce. Is this a wall with some special anti-spin coating like some table tennis rubbers?