What I did was look for something unique for the page in your code and saw your postid in the body section of your source code. So you can add that post id code next to the .wrap
and it will override anytime that page is used. Try adding this to your css to see it work –
.postid-2498 .wrap {
max-width: 1140px !important;
}
Just add it in the main css and not the responsive section so it will always be activated.
You can also hover over your post/page link in your admin section to find out the post/page ID instead of looking in your source code. More info – https://wordpress.org/support/topic/where-can-find-the-post-id