It seems to me that you will not be storing the correct inventory id in your order details. Regardless of what items are purchased you will always have the same inventory id stored in the db.
To get it storing the inventory id for the specific item you would need to do some customizing. It would probably be easiest to add the recordset inside of the loop for the store order details server behavior. Then just filter it on the item id. This part is a little custom and will require some hand coding inside of the store order details.
You could also have a column in the cart to hold this value, then just store the value from the cart column rather than the recordset.
