Words cannot express how much I love this poem, but I shall try my best to leave a review. The fact that it's still reviewless makes me very sad.
You really capture not only Dudley, but his entire world, which is so very small of course. I think every line is particularly apt but there are a few that stand out. I love the idea of Dudley's house being bigger than his imagination. It's a great way to describe the inanity of his life, the bubble that he lives in, seeking nothing more than what's put on his plate by Petunia. "Increasing waste, increasing waist" is a great play on words. The funhouse mirrors in Petunia's eyes is also wonderful imagery, and the final line is such a solid way to sum up the entire poem.
The way you structure the poem, using "In my house" at the beginning of the second and third stanza lends a lovely rhythm to the poem, which you always do so well in your free-verse poems. I loved setting this challenge, and your entry was a well-deserved winner.