I should be accostomed, by now, to looking at a premise and a pairing and wincing at my own thoughts of how it would work, then reading your interpretation and being delighted, but it seems that I am not jaded yet.

For something "doggerel-y" as you say the sonnett is very admirable. The repetition of the idea of the heart as lead, the surprise of whimsey at the end. The spondee of "it skips" lends to the idea of Snape's surprise.