I love this so much! You've made drawing seem to be a natural extension of Childermass's history and personality that blends in perfectly with the character we already know, and showing his development as an artist throughout his lifetime, and the different ways he used those skills, was a really interesting way to structure this fic. I like how you've acknowledged the fact that drawing takes time and work, and the fact that being good at drawing people, which Childermass practices a lot, doesn't necessarily mean he'll be good at drawing other things like landscapes.
I also really liked the contrast between parts 4 and 5 in Childermass and Norrell's relationship, and how Childermass views his job and his master.
Finally, I like the ending, where Childermass takes the time to visit wild places and learn how to draw them and understand them. It's so poetically written ('wrestle the aching land onto paper'! I'm in love!), and it seems like a really fitting ending for him, now that magic has returned to England and Childermass has... I don't know, I guess the freedom to live up to his potential in ways he couldn't before? Basically, I love it. The little nod back to his childhood of using pictures to tell stories was lovely too.