As someone who has a cat who had bladder stones, I feel your pain. I would suggest using an enzymatic cleaner (Nature's Miracle or Got Pee) instead of the vinegar because even if you can't smell the pee after using the vinegar, the cat can and they will continue to pee where they smell it. Nature's Miracle can be found at Petsmart or any other pet supply store. I had to order Got Pee online. Got Pee is more expensive, but it worked better for us.
Regarding the diet, I would leave the cat on what your vet recommended until the stones are gone and he's urinating in the box instead of around the house. Then I would go to your local store and ask for opinions regarding other options. We have our girl on a grain free dry food, we supplement with wet food, and she gets a cranberry supplement in her wet food. It's a powder, we just mix it in. It's worked for us.
The water fountain is a good idea, we have one of those too.
Good luck! I know how frustrating this can be!