When Cordelia prints the invoice, the 'O' is not proportional to the rest of the word. The word is spelled with a zero: 'INV0ICE' However, as this is Cordelia, it's likely that she wouldn't even have noticed that she pressed a zero instead of a letter 'O', especially as Angel specifically says that Cordelia "can't type or file" in Rm w/a Vu.
When the torturer captures Angel by slinging a chain round his neck, Angel is seen writhing and clawing at his neck even after the initial shock, even though vampires don't need to breathe in the Buffy universe. However, choking would still be painful.
Fire accelerant is visible on Angel's back when he runs into the sun and catches on fire.
(at around 1 min) While Doyle and Cordelia are searching the dark, unlit sewers, lamps/lighting equipment are visible in the bottom right corner of the shot.
When inspecting Angel, Marcus the torturer makes a remark about the lack of external damage on his skin despite all the centuries he's been "alive". This is at odds with later episodes revealing how Angel has repeatedly been tortured and maimed before, for example t Holtz's hands in the third season's "Offspring".