Without sitting down and writing all of the custom code for you it is going to take a while before I can ...

You should be able to use a lot of the code that I posted to search for the coupon code on the order and then display the coupon_description on the pages that you need it ...

For the account_history_info, I think you can access the orders_id with:
$_GET['order_id']

And for the orders.php in the Admin, I think you can access the orders_id with the:
$_GET['oID']

see if that doesn't help you get the information that you need ...