Well, as you can see, I ended up having enough yarn to finish. I do like the short sleeves, too, so I'm calling this a success, overall. My only qualm is that the button pulls a bit which makes me think I should have made the bust slightly bigger, but I'm wearing it with a pin right next to the button and that seems to do the trick.
I wasn't going to block this project (laziness), but in the end, I ended up doing so. I'm glad I did as it seems to be lying better and the button-pulling is way less pronounced.
Lovely pattern! I see many more top-down projects in my future.