Ok well it seems you have covered everything then hehe. I don't know what else to suggest. Other then buying something like Natures Miracle to pour directly on the carpet to soak. I don't think I have any other suggestions
I am still going to comment on the food though if you don't mind. Friskies is junk food and an all dry food diet is not always best. Wet is more like their natural diets. Vets are not nutritionists and often recommend what they sell or what is easiest simply because they don't really know much about diet and nutrition.
You really might want to do a little research on cat health and nutrition. It is very simple to find healthier foods that aren't junk. You can buy a large bag and it will last a long time if money is a concern. Grocery store foods are junk and even if the cats are healthy now, it usually results in more health issues, more vet visits and more money as the cats gets older. Just keep that in mind. Sure it is easier and cheaper to by the low grade crappy food at your next trip to the grocery store. But it is also easier to run thru McDonalds drive thru everyday, every meal, isn't it? A lot of people don't look at it that way
I would much rather my cats eat healthy meats and good ingredients and vitamins instead of by-products, pieces and parts of various animals and corn fillers which don't keep them hungry but makes them keep wanting more and more which also means you are buying the food more often. The higher grade foods last much longer, especially if you buy a large bag.
Just think about it. I won't keep bringing it up since that is not the topic here. Well eventually it could be but it probably isn't right now
P.S. My one cat will not stop peeing on the nice pretty expensive bathroom rugs from Dillards.
I know just how you feel. I either keep the bathroom door shut or pick the rugs up.