Uploading images from a custom page using blueimp uploader?

After doing tests and working with a friend I was able to find a solution:

Just change how the function get_full_url grabs the url:

// Go to 'protected function get_full_url()'
// Line 200 (approx. if you've made the same changes stated above) in UploadHandler.php 
// change this line, should be the last one in the function
substr($_SERVER['SCRIPT_NAME'],0, strrpos($_SERVER['SCRIPT_NAME'], "https://wordpress.stackexchange.com/"));

// After editing this is what you should end with
substr($_SERVER['DOCUMENT_ROOT'],0, strrpos($_SERVER['DOCUMENT_ROOT'], "https://wordpress.stackexchange.com/"));

This is what worked for me (along with the customized code from the question), allowing me to use the demo uploader in a custom WordPress page. Creating a frontend upload form! Hope this helps someone.