Spoke too soon!
Apparently the issue didn't get fix and now I know why.

I modified the tpl_modules_opc_submit_block.php and added that block of code to prevent the checkout button from showing up if the order didn't reach the minimum amount $100 for free shipping. With the regular checkout it works, and it works with OPC as long as the amount is above $100. However in testing with lower amounts that's when I get the error and I have no clue how to make it work.

Code:
<?php
// -----
// Part of the One-Page Checkout plugin, provided under GPL 2.0 license by lat9 ([email protected]).
// Copyright (C) 2013-2017, Vinos de Frutas Tropicales.  All rights reserved.
//
// Check to see that at least one shipping-method and one payment-method is enabled; if not, don't render the submit-button.
//
if ($shipping_module_available && $payment_module_available) {
    // -----
    // Set up two form-submittal buttons, one for payment methods that require confirmation and one for those that don't.
    // This page's header_php.php has created an array of payment modules that require confirmation, which is pulled into the
    // page's jscript_main.php.
    //
?>
<!-- bof disable checkout button from displaying 1 of 2 -->
<?php
if (!IS_ADMIN_FLAG) { 
  global $order; 
  if (($order->info['total'] < 100) && is_object ($freeoptions)) { 
	echo '<div style="border: 3px solid #777777; padding: 10px 0;"><p style="text-align: center;"><strong>Your order does not qualify for Free Shipping at this time.</strong></p>
	<p style="text-align: center;"><strong>Please go back to the - <a href="index.php?main_page=shopping_cart">SHOPPING BAG</a> - to add more products or increase the quantity of products in your bag to meet the minimum order amount required to qualify 
	for free shipping,</strong><br /><strong>or select a different shipping option.</strong></p>'; 
  } else {
?>
<!-- eof disable checkout button from displaying 1 of 2 -->

<!--bof submit block -->
  <div id="checkoutOneSubmit" class="buttonRow">
    <span id="opc-order-confirm"><?php echo zen_image_button(BUTTON_IMAGE_CHECKOUT_ONE_CONFIRM, BUTTON_CHECKOUT_ONE_CONFIRM_ALT, 'name="btn_submit" id="btn_submit"'); ?></span>
    <span id="opc-order-review"><?php echo zen_image_button(BUTTON_IMAGE_CHECKOUT_ONE_REVIEW, BUTTON_CHECKOUT_ONE_REVIEW_ALT, 'name="btn_submit" id="btn_submit"'); ?></span>
    <?php echo zen_draw_hidden_field('order_confirmed', '1', 'id="confirm-the-order"') . zen_draw_hidden_field ('current_order_total', '0', 'id="current-order-total"'); ?>
  </div>

<!-- bof disable checkout button from displaying 2 of 2 -->
<?php } } ?>
<!-- eof disable checkout button from displaying 2 of 2 -->

  <div class="clearBoth"></div>
<!--eof submit block -->
<?php
}