The important thing to consider when deciding to replace the voltage regulator vs. alternator is the mileage. With the regulator removed you need to take a close look at the stator shaft. This is often overlooked. With high mileage the shaft wears considerably at the brush contact area. Just take a peek up inside of the alternator. If the shaft is worn there's an obvious difference in the color at the contact area. A close look will determine the extent of the wear. As far as the fuse in the OVP not blowing, it's not the voltage, but the current that burns out the fuse. In this case the OVP did it's job, which is to protect critical (expensive) control modules from being damaged. Finally, I'd suggest removing the battery tray and neutralizing the battery acid, which most likely wound up down there following the battery boil-over.