After 23423865873 more attempts, I defeated Gergorio III. Just. I had no energy left at all. Hurrah!
The next round was really easy, and I finished that on my first attempt, before moving on to the end of game boss – who was probably the easiest character to beat in the entire game! Not only was it a simple hammer-the-button for the “strum” cues, but there was a “charge” section every minute or so, which allowed me to regain all of my health. So I beat him, and the game was won! BEST.
And I’ll never play it again, because it is crap.