How much fish or is any fish too much?

I am trying my best to get my male cat to eat his Royal Canin Urinary canned food. He had a blockage about 2 weeks ago. I have tried sprinkling and mixing several things in his food. At best he will eat about 1 can a day which is not nearly enough.

I read about these Salmon freeze dried treats called Pure Bites so I have been sprinkling some on his food. If I do this every time he eats is this going to be too much fish in his diet. It becomes the 'lesser of two evils' really. He needs to eat this urinary food. I know some believe he would do fine on just canned food alone and not a prescription diet but I don't want to take a chance.

Freeze dried fish treats on top of food daily is in my opinion not a lot of fish. I put fish treats on top of all my cats food almost daily without issue. I understand your perspective on the RX food, but if he wont eat it, he wont eat it. He's better of eating some wet food he likes in addition to the RX food than not eating enough of his RX food, losing weight, and having other medical problems. So you have to pick your battles.

You can also try crumbling a bit of freeze dried raw on top of his food. It's pretty smelly so cats seem to really like it. 

Have you tried adding a water fountain also to increase water intake?