Reading settings in the home page precisely home.php

I modified your code just a bit. See if this works

 if ( ! function_exists( 'the_post_limit' ) ) {    
        if ( true == get_theme_mod( 'the_post_limit', true ) ) {    
            function the_post_limit( $query ) {   
                if ( is_admin() || ! $query->is_main_query() )    
                    return;    
                if ( is_home() ) {    
                    // Display only 1 post for the original blog archive
                       $get_default_posts_per_page = get_option( 'posts_per_page' );
                    $query->set( 'posts_per_page', $get_default_posts_per_page );    
                    return;    
                }    
            }    
            add_action( 'pre_get_posts', 'the_post_limit', 1 );

        }

    }