I think you can update the condition of your function remove_add_cart_button
to check for products, something like the code below:
/**
* Remove add to cart button
*/
function remove_add_cart_button(){
// Products
$product_ids = array(110, 111, 112); //todo: put your product ids here
if(in_array(get_the_ID(), $product_ids)){
remove_action('woocommerce_single_variation', 'woocommerce_single_variation_add_to_cart_button', 20);
}
}