I'm sorry it seemed the novel didn't strike a chord with you. Was excited to see your reaction to it a lot but... Yeah. Anyways, to address some of the issues, I really don't know how else I could've framed it. It was mostly supposed to be a retrospective on a life snuffed out and Memento being present as Mori dies I think would've had some logistical issues like does everyone get a reaper that appears before you before you die or other stuff that I think would've overcomplicated the kind of story I wanted to convey. And, I would like clarification on the second part about Mori's second death being less poignant? I don't understand this section because Mori died once, and psychopomps are beings that take the spirit to the after. It is a "second death" in some sense but it was more the erasure of Mori's soul and consciousness. His first death the erasure of his physical being, the second himself.
As for the last part, Memento and Mori never had a genuine romantic relationship like long time partners would. It was, a fleeting moment of intimacy between a being that's experiencing it for the first time and a man who has longed for someone to be close with. It wasn't really a romance in the conventional sense, but a romantic experience that they simply shared.