An excellent story. I liked the sparse style; the way Rufus starts off narrating about his training as if this might be a textbook, not the memoir of his own death - you show us the admirable self-control he has in your prose.
I think you drew Rufus very clearly as a character here - unapologetically ambitious and solitary, yet also fundamentally a decent and principled man. I particularly liked this line:
...who has lived such a male life, full of Unspeakables, of cigars in back rooms and fifty-year-old Firewhisky by the mantelpiece - it strikes him as ironic that the memories that come to him now are of women.
...and this section caused a sharp intake of breath:
That had shattered him inside, seeing his lovely Emmy laid out like a Niffler ripped apart by a Kneazle... Driven by fury, he hadn't even realised that he'd fulfilled his final ambition until he'd read about it in the Prophet.
I also found it very interesting the way that Rufus seemed to call the shots within a relationship, and then was faintly surprised each time the woman decided to end it. A very fitting detail about the way his mind works - blind spots and all!