I'm not sure of your question so are just trying to get the pulley off?
That allen bolt you are talking about is actually part of the shaft of the power steering unit, the pulley is pressed on to that shaft. It requires a special tool to pull it off but if the pulley is broken you may not be able to pull it off. Pic below
There could be from the heat if you got the front seal to hot.
The threaded screw is just to install the new pulley and should fit right through the center of that allen hole and screw into the pump shaft.
Positive feedback is always welcome