Adjust Width of Article Title Boxes on Home Page

How do I make the width of the gray boxes that display the article titles equal to the width of the photos beneath them on the homepage of The photos become smaller as the screen becomes smaller, so the gray boxes should always be the same width as the photos (even as they photos become smaller). If the gray box ever gets too small to display the full post title, then I'd like it to display as many characters as possible and end with "..."

I have granted support access via the wpmu plugin, in case that helps!

Thanks for your help!