The VISA promo code doesn't apply to the lowest R fares apparently. But if you've run out of R and are now looking to fly in I, it'll knock down the price 15%. I had this happen to me on an outbound leg (don't have flexible dates, and wanted to lock in the 5X miles) just now and the promo code helped bring the price down a bit.
For the 5X miles, log into privilege club and register for the offer under My Offers. Then make sure you enter your number while booking. Of course, 5X is now off the table. You can get 4X though. Not too shabby.