hover post title over image

I’m working on a WP site where I’m using CSS multicolumn to create a masonry effect for the blog index page.

I’ve got it working mostly, but I’d like to hover the post title over the image (the post thumbnail) instead of having it show above the image.

I’d also like the image to fill the whole column container, and currently it’s not doing that, even when I’ve set a width to 100%.

I’m kind of stuck at this point, and not sure how to do this. Anyone have advice?
Here’s a link to the test site: https://tippingpointphoto.flywheelsites.com/blog/