I'm pretty sure Fiona is closer to 150% complete.So based on the Demon King's description, even if Albus speedrun the entire journey way faster than the last loop, it won't be enough because by now Fiona is kinda 90% complete so to say. Basically Albus will be late every single time.
The only way to make sure Fiona alive is to dispel that blessing before killing the demon king or seal it the moment it came out from Fiona's brother (hinting at the consequence of time looping?)
I wonder if they, like everyone else in contact with time looping albus, is reg/taining memories. But because of their immortal soul they're mistaking those memories for past incarnations. So they've just been really slowly becoming senile, probably more rapidly from the timelooping.It only makes sense that the demon king has an idea about how he got beat everytime.
If everytime the hero somehow can overcome you, you start thinking of the possible cause and the looping is one.
That said, it is interesting that the original demon king and hero were some kind of mortals which changed themselves due to their obsession (at least that was the case for the demon king). This begs the question of the existence of the one which grants heroes their looping ability.
All in all very interesting plot development.