Hello,
Try adding this CSS in your Custom CSS (Appearance > Theme Options > Styling Options > Custom CSS) for adjusting the width:
.main-container {
width: 1140px;
}
#page, .container {
max-width: 1140px;
}
.article {
width: 68.2%;
}
.main-header {
max-width: 1140px;
}
Then for adjusting the Featured thumbs, you need to edit the values of the thumbnail size from the functions.php. For that you need to go to Appearance > Editor > functions.php and look for this code there:
add_image_size( ‘bigthumb’, 620, 315, true ); //Big thumb for featured area
add_image_size( ‘mediumthumb’, 300, 200, true ); //Medium thumb for featured area
add_image_size( ‘smallthumb’, 140, 100, true ); //Small thumb for featured area
Here you can adjust the width and height so that you can see the featured images fine also.
At the time of editing the core files, make sure you are using a Child Theme so that all your changes remain safe even after update.
Hope that helps.
Thank you.