Slughorn/Benjamin: new OTP!
I'm utterly in love with Horace Slughorn. He has the subtle canniness and capacious knowledge that befits a Head of Slytherin - and given that he *was* Snape's Potions teacher, I adore how readily he picks out that tell-tale scent. Also, I adore how smoothly he reveals it. He's smooth all the way through, but your hint of his inner loneliness (not that he can't cope) is so achingly beautiful!
He's like one of my favorite characters from a Georgian-era Georgette Heyer, always urbane but utterly ruthless, hiding a gambler's nerves behind his carefully cultivated appearance of drollery. I love him!
And I think Benjamin Jinks can love him, too. As your backstory makes sadly clear, they should have discovered each other's inner merits a long time ago. Curse Riddle for having made Slughorn too cautious! And Lily, and the others, for overshadowing Snape in school.
I love that it's in Vancouver they meet - a darkly rainy city in the winter, but one that always has a heart of warmth and magic. That makes it such an appropriate place.
P.S. I would dearly love to see Horace take Benjamin to his tailors! Their repartee is so gracefully turned. I'd take any additional lines of it I could get. :D