Okay, so for my first tip. This part here:
I think it makes him more reasonable, his "exception". I mean, I feel people in general are all a little jaded of characters with unbreakable convictions, with like, Ned Stark, and stuff.
There's a saying: "The difference between fiction and and non-fiction is that fiction has to make sense."
What that means is that in real life, people change their minds all the time. They behave irrationally. They can be "reasonable" and change their minds in order to please others. Sometimes they make important life-changing decisions without thinking them through. Yet, we do not yell at God that he's "writing" them out of character.
Decisions that fictional characters make have to make sense in the context of the personality the writer his given them. When a character makes an important life-changing decision it has to be "earned" by the character having grown into a new understanding of the world. Galio can't just decide to accept Lux's help because he hates to see her cry or because he's making her sad. It's clear throughout the book that emotional responses are not enough to cause him to change his position on necromancy.
Poppy's argument that he's pointlessly martyring himself has traction because that's exactly what everybody told him in his first life about Dederick. Learning from his previous life could have given him the insight to acknowledge that his usefulness does not have to lead to a pointless death. But I didn't set it up well enough and the ending isn't quite as earned. There's a kernel of it there, but I could have done more.
The idea of characters "earning" growth is so important because otherwise your story is just about people doing things and it's hard to become emotionally invested or attached to any of the characters. How can you when they could just suddenly change their minds? This is one of the reasons why everybody was upset about what Jayce's lore did to Viktor. The sudden shift of Viktor from a bitter victim of intellectual theft to also turning out to be a thief wasn't earned. There was nothing in what we know of Viktor to indicate that he would cross that line. In fact, what we knew suggested the opposite. It appeared to be behavior that was beneath him. And so Jayce's lore needed to be changed, and it was.
Also, Ned Stark did eventually see reason, didn't he? And how did that work out for him?