Great depiction of Goyle -- I can easily imagine him liking to work with his hands, growing to take pride in a job well done, even adapting to Muggle life because it's easier/better than constantly fighting. The relationship with Millicent develops in appealing ways; they are very well-matched.
And wow, do I want to eat about fifteen different kinds of bread/pastries now!
“But none of them are wearing blue and walking with me.”
Perfect! This line sums up your Greg for me: pragmatic, realistic, willing to take the good things life gives him, with a sense of humor deep down. His is a different sort of ambition from the usual power-gathering sort, but it's believably Slytherin all the same.