"I couldn't help overhearing what you and Malfoy were saying ––"
"Bet you could," Ron muttered.
"––and you mustn't go wandering around the school at night, think of the points you'll lose Gryffindor if you're caught, and you're bound to be. It's really very selfish of you." "And it's really none of your business," said Harry.
"Good-bye," said Ron.
All the same, it wasn't what you'd call the perfect end to the day, Harry thought, as he lay awake much later listening to Dean and Seamus falling asleep (Neville wasn't back from the hospital wing).
–– Harry Potter and the Sorcerer's Stone
[i] Is the highlighted part a fused relative (or free relative)? I guess what in ‘what you’d call Ø the perfect end to the day’ is a fused relative. But there being a dummy it, I’m not sure.
[ii] Is ‘as’ a conjunction for saying the reason of aforesaid words?
[iii] Is 'to the day' an idiom, meaning 'exactly"?