It should be Weasley's Wizard Wheezes, not Weasley Wizard Wheezes. It should be Mundungus Fletcher, not Mundugus, and Horace Slughorn was also a headmaster of Slytherin. Other than those, a fun quiz.
I should have phrased that better...Snape and Phineas were the only two headmasters of Hogwarts from Slytherin. Slughorn took over for the head of his house,slytherin, when snape became headmaster.