page featured image width

On a full width page layout, the featured image automatically gets resized to 810px (“?810” at the end of the image url + width attribute set on the <img> tag)
The problem is that for full width pages, the main content container goes up to 1140px in width (larger screens), so a 810px image there looks pixelated.

This is due to functions.php, line 50.
The “nucleare-normal-post” image width should be “1140” to accomodate this size. With a smaller page width, it will still be fine, just higher resolution.

I’m using this theme on wordpress.com, if a fix is done to this theme, how and when would I get it?
wordpress.com does not allow me to modify the theme php files unfortunately, I am solely depending on your help there to get this issue solved and be able to complete my website.

Thanks a lot!