Hi,
This is due to how the WordPress loop takes the current post ID from the last post in the list on the blog page, so the sidebar options won’t work on the page you have set to display your latest posts.
You can work around this by adding a small snippet of CSS;
if you are using WordPress 4.7, go to Appearance > Customize > Additional CSS and add this:
.blog #primary{width:100%;float:none;}
if you are using a version of WordPress older than 4.7, you could install a custom CSS plugin which allows CSS per page/post such as https://wordpress.org/plugins/wp-add-custom-css/ and on your blog page add this:
#primary{width:100%;float:none;}