You can prevent the wrong card type from being tendered by setting a Validation Mask.
In SO Manager, Database/Tender Types Open the properties of the "Visa" tender type Go to the "Verification" Tab in the "Validation Mask" field enter "4*" (without the quotes) This means that only account numbers starting with "4" will be accepted for the Visa tender type. Do the same thing for all of your CC Tenders: Visa = 4* Master Card = 5* AmEx = 3* Discover = 6*
You can prevent the drop/payout problem by limiting the cashiers allowed over/short amount and making them balance their own drawer. Go to Cashier Properties and enter either $0, or some very small amount that you are willing to accept as out of balance in the "Limit Amount" field under "Over/Short Limits" (this defaults to "No Limit").
To deal with a forgotten Pay Out, you could enter the Pay Out as part of the following Batch (the only place that you can enter it anyway) and add that amount to the Closing amount for the blind closed batch. All you can really adjust after teh blind close is the opening or closing amounts.