How does putting a new fuse in, verify it's the motor? It might be the motor, but couldn't it instead be the control circuit in the ABS module? A more definitive test would be disconnect the motor and test it, or then put the fuse in without the motor connected. I suppose it's also possible that a rodent or other wear could be shorting out the wiring to the relay for it, and while it's not a definitive test, if you unplug the ABS module connector, and put a fuse in, and it still blows with vehicle running, you know there is some other cause than the module.
I haven't heard of anyone replacing just the motor but it seems like it should be possible if you can find one. I would have guessed that all you will find is old/used ones pulled off a bad HCU and I wouldn't want to bother using one that was potentially in service for over 20 years already... though I can appreciate fixing things inexpensively so I suppose it depends on what a junkyard wants for one... I wouldn't pay dozens of dollars plus shipping for something off ebay and don't know if you need some additional gaskets or other seals too.
If you get to the point where you know for certain you need to either replace just the motor or the entire HCU, at that point it seems like there's no further risk to go ahead and try to extract the motor to see if you find any problems in putting it back into working order with a different motor.
I don't even recall, is the motor bolted on, or riveted? I suppose in most cases, rivets could be drilled out and replaced with bolts.
