Past life commentary, because we've talked about most of this other stuff in Discord: I like #1 personally, because I think it fits better with this particular flavor of OP. Since his present life is relatively chill and humble, I think having a past life who was a paragon of virtue with accomplishments to want to live up to would work really well for him. It's a convenient hook for any future crises of faith/conviction (a great potential manifestation of OP going into eclipse, imo).

Since his military career was derailed by the arrival of the Abyss, do you think he could have gained an initial reputation for leadership etc by participating in the fighting before he escaped aboard the Nashira? You def don't have to decide now, but I think some more fun food for thought about his past life is thinking about what he was doing during the relatively brief period when they were trying to fight back against the Abyss.