Create WooCommerce Discount and Stock Quantity functionality Urgent

Hi, I've a Wordpress site, where a user can edit an already placed order depending upon the status like "On Hold". When the user edits the Order, he can add/delete product quanity, add a new product, and save the cart. All this functionality is in place. However, only couple of things are left that needs to be done now. 1. Right now a user can order X no. of quantity, however, I want you to restrict the user to add more than available quantity. For example; if there are only 20 items available, a customer entering the 30 items, should get an alert that only order for 20 quantity can be placed. 2. Currently the discount system is also active which is applicable on total cart value. However, there's some technical glitch into it as it shows more discount...but correct total billed amount. So you need to fix that as well. 3. Display the Discount attained in the order summary. WooCommerce, jQuery and Ajax expert can do this task in maximum 4-6 hours. as the previous developer did all the work in 1 day. Only serious bidders with good profile to back their bids need to apply. Will close the project in maximum 1-2 hours if I find the right guy.