In your custom layout, yes you’ve got the full-width sidebar layout applied, however in that full-width area you have the “Columns” element; you’ve got it setup with 2 columns (66%/33%).
You could do two things that could quickly give you the result you’re going for.
Option 1: Set the Columns element to “1 Column”
Option 2: Copy the content from the first column. Delete the columns element. Add a “Content” element. Paste in the copied content.