I'm confused with Itsuki now.
I feel like stopping her from having the sure-fire death surgery was the best result. There's only a "chance of success" when something is actually changed about an otherwise predetermined scenario, so "blaming himself" for her not having the surgery as though he stole her small chance at victory is kind of weird when he appears to know, unaltered, his visions aren't wrong. It's kind of weird how he's characterized so strongly implying you can't change fate when he in fact already had a huge success with that woman, having no doubt lived longer than she would have otherwise. She wasn't cured of her ailment, but that wasn't what was going to kill her in the first place. We have no idea how long she has/had, but everything about her life after skipping out on that surgery could be seen as a new branch of fate. She could even have the surgery at a later date and may well survive (or not). But he threw a wrench in her predetermined death and at least stalled it.