Wait for JQuery execution until whole page is loaded breaks execution

I have a JQuery script to load a newsletter subscription popup window after the users scrolls down a certain amount of pixels using the jQuery .scroll/.scrollTop function.

At the moment it's all encapsulated within

jQuery(document).ready(function($)

The problem is the usual caching and images issue and the subscription box pops up all over the place. I was reading about delaying jQuery using the .load function until the page is fully loaded. However when I replace

jQuery(document).ready

with

jQuery(window).load(function($){
  //your code here
});

the functionality breaks completely.

I want to note that I am using WordPress and have the script enqueued like this:

function enfold_child_custom_scripts(){

    // Register and Enqueue a Script
    // get_stylesheet_directory_uri will look up child theme location
    wp_register_script( 'custom-js', get_stylesheet_directory_uri() . '/custom.js', array('jquery'));
    wp_enqueue_script( 'custom-js' );

}

add_action('wp_enqueue_scripts', 'enfold_child_custom_scripts');

Here is my JS/jQuery code as it is right now.

jQuery(document).ready(function($) {

    jQuery("#nl-pop").hide(); //hide nl block initially
    var disableFade = "false";

    var startShowTop = jQuery("#newsletter-cta").offset().top - 3500;
    var startHide = jQuery("#newsletter-cta").offset().top - jQuery(window).height(); //Hide when the viewport is reached

    jQuery('#no-thanks').click(function(event) {
         event.preventDefault();
         jQuery('#nl-pop').fadeOut('slow');
         disableFade = "true";
    }); 
 jQuery(window).scroll(function() {
        if(jQuery(window).scrollTop() < (startShowTop) ) //when scrollposition is smaller than the first point
        {
             jQuery("#nl-pop").fadeOut(200); // Hide when in the upper part of the page
        }
        else //when reached the lower part of the page
        {
            if(jQuery(window).scrollTop() > startShowTop && $(window).scrollTop() < startHide && disableFade==="false") { //When reached the show position but not as far down as the hide position
                jQuery("#nl-pop").fadeIn(200); //show
            }

            else if(jQuery(window).scrollTop() > (startHide) ) { //scrolled down to the bottom newsletter box
                jQuery("#nl-pop").fadeOut(200); //hide
            }
        } 

    });   
});