We are very sorry that you are facing this problem at the crunch time.
The fact is that the OSX updater on MAC was tested on 6 different MAC’s with different operating system, which include 10.8, 10.85, 10.9 and 10.10. We never had any problem. But, recently we have had a couple of complaints regarding this and there seems to be some problem which we did not find in the lab during testing. We will try to get to the root of the problem and get it fixed in the near future.
In the meantime, as a work-around, could you find another MAC or Windows PC with which you can do the update of the firmware. Remember that the Windows PC requires a driver installation before you can use the update package.
Once you manage to get the update done, you can reformat the drive using the LP-16 and export your songs again.
I hope things get sorted for you before the show.