[GT3 Pure Theme] Remove featured image

I am trying to remove the featured image from the top of each post. I am using the Pure Theme from gt3 themes. The featured image shows up at the top and shoves all the other content to the far right.

I have tried installing the remove featured image plugin, while the tickbox shows up clicking it has no effect. I have also tried editing the page.php and single.php pages within the theme as suggested by several other posts. But the lines they call to be removed are not present in my code (or at least I have not located them). The only code I am seeing (inside singel.php) related to the featured image/thumbnail is:

$featured_image = wp_get_attachment_image_src(get_post_thumbnail_id(get_the_ID()), 'single-post-thumbnail');

I have tried removing this with no effect. I have also tried adding something like this to the css

.featured_image_standalone {
display:none;
}

Also no effect. I have a few clients that use the Avada plugin and I have managed to disable the 1st featured image with no problem but I am hoping for a free alternative to purchasing this plugin.

Alternatively, I would be satisfied if I can add additional images below the featured image, leaving the copy to the right. Like on this demo page.

Any help is greatly appreciated! I am a beginner but have been editing/managing WP sites for clients for several months now so I’ve gotten my hands dirty and with a little instruction I am sure I can remedy this issue.

My site is https://jazmynfaulkner.com/ but it is currently in maintenance mode.
Thanks!