That is fantastic to hear. That is a clever way of getting the uses recorded, I'm glad that you found a way to do it. There is one part of this that leaves it open to possible user interference. Since you are setting the hidden form element to the $coupUpdater value a user could potentially alter this value. If the user were to add 50 to this hidden form element value it would essentially give them another use of the coupon.
I think the best way to get around this would be to reference the variable value directly in your update. You should be able to view the code for your update and see where it is using the hidden form element, if you replace the hidden form element value with your variable it should ensure the integrity of the uses of the coupon without any potential user interference.
As for the problem you are having remotely it may be a good idea to back up what you have on the remote server then ensure that you upload all of your currently working local files to the remote server. This should get you the same result on both assuming that everything else like the connection is working correctly.