Logo Shrinking Too Small

shrinking amount is outsourced in an own js file: avia-snippet-sticky-header.js

so you can have that file on child-theme. Create a folder js under enfold-child.
put in a copy of that js file: avia-snippet-sticky-header.js

Put in your child-theme functions.php:

add_action( 'wp_enqueue_scripts', 'wp_change_sticky_header_script', 100 );
function wp_change_sticky_header_script() {
   wp_deregister_script( 'avia-sticky-header' );
   wp_enqueue_script( 'avia-sticky-header-child', get_stylesheet_directory_uri().'/js/avia-snippet-sticky-header.js', array('avia-default'), $vn, true);
}

open that copy in your child-theme and edit the lines 64 and 76:
(click to enlarge)

you see that on standard shrink behavior both values are 2 (that is a special case because scroll-distance is the same value as endpoint header height / if you start at 200px you must scroll 100px to reach the 100px end height)

shrink only 33% – the first divisor is 3 ( line 64 )and the second one ( line 76 ) is 1.5

shrink only 25% – the first divisor is 4 ( line 64 )and the second one ( line 76 ) is 1.33