After several months of working on and off, I finally finished the sweater. It's not quite the same. I am really not sure how well it will fit since I didn't have a decent size reference or pattern, but hopefully it works well enough for his purposes.My computer was being stupid and rotated the picture. I didn't feel like figuring out how to fix it, so please turn your head.
I plan on giving him the sweater at Thanksgiving so he can wear it before the actual holiday for any ugly sweater parties he might have. I'll try to get a picture of him in the sweater once I've given it to him.