GIMP :: Coloring Outline Drawing And Removing The Outline?

I have a black-and-white outline drawing that I want to color in using the "Bucket Fill" tool. There are two things I'd like to do to make it easier:

1. Is there a way to prevent Bucket Fill from leaking through small gaps in the drawing? Usually what happens is, I fill in one region, and then suddenly a much larger region gets filled in. I then have to examine the borders of the region for a small opening, close the gap with black, and then try again. Is there a feature that lets me say e.g. "Don't fill through gaps less than 4 pixels wide"?

2. Once I'm done coloring, I want to remove the black outline to make a more realistic, less cartoony image. However, it's tedious to go and paint over every segment of the outline with the color of its adjoining regions. What I want to do is essentially: Replace every black pixel in the image with the color of the closest non-black pixel. Is there a feature that does this?

Also, if there are third-party plugins that do these things, that would work just as well.