Reply To: Center and enlarge the featured image under the post title on the homepage

Good morning,

Line 54 of functions.php it control the excerpt thumbnails size

add_image_size('excerpt-thumbnail', 200, 140, true); // Sets Index Page Thumbnails

You can try changing the numbers 200,140 to 665,300 to get bigger image so that content will be below the image.

After making the above change you will have to regenerate thumbs once https://wordpress.org/plugins/regenerate-thumbnails/