It's now a given that the pump assembly will need to be removed from the car. After removal, you can try a few things things:
1) Cut away the pulley with a die grinder, then carefully slit the hub and pop it apart with a chisel. You want to cut through as much of the hub as possible without getting into the pump shaft. And, be carefull banging on the hub so that you don't damage the shaft/bearings/seals.
2) Cut away the pulley as above, then heat the hub to expand it and pry it off, or use a 3-jaw puller. You can also drill holes in some of the remaining pulley, and use a piece of all-thread and nuts to pull on. You'll need to be careful not to over heat the hub/shaft and ruin the seals.
3) Place the pump assembly in a hydraulic press, support the back side of the pulley with some steel straps, etc. then press down on the shaft. This is actually pressing the pump off of the pulley.
That's all that I can think of right now...
JD