Hi John,
There is a default 3% left and right padding in the content area of the blog posts that you can override through custom CSS so kindly add this code in X > Theme Options > CSS:
.single-post .entry-content {
padding: 0;
}
You may also disable the column container of the Row setting to have the content of the sections fill the entire content area:

To further increase the width of the content area, you may add this CSS code as well:
.single-post .entry-wrap > .x-container {
width: 100%;
max-width: 1350px;
}
Kindly note that since this is a custom code that changes the default behavior/display of the theme, you will be responsible to maintain or update the code in case you require further changes or if the code stops working in future updates. If you are uncertain how to proceed, it would be best to get in touch with a developer.
Hope this helps.