Not meaning to sound like a stickler, but I think Vernon's using the word "mutt" a little too much. Also I think Harry would definagely fight back.
I love the line "and so he slumbered, a prisoner in his house, but even more so in his mind." Plus, the imagry and details you used really enhanced this story, making me feel more than a little afraid of Vernon's wrath. Keep up the good work!
I was beginning to think you had abandoned this. I hope you have a nasty end for Sniv.