Thank you for the screen shot! Instead of the current styles try this:
Go to your Dynamic list settings and set the posts to span full width instead of in two columns.
Then go to your "Latest Blog thumbs" class and set it to be, display: block, about 48% width, no margin on either side and set to float: left. Remove the height settings as they won't be needed anymore unless you need an exact uniform height on each one.
Here's a screen shot of those styles in the designer:
Be sure to adjust the widths of the thumbnails accordingly on the next breakpoints for the responsive design (100% would take up the full width ) Please let me know if this helps or if you have any questions