You might talk to your urologist about
trying some different phosphodiesterase 5 inhibitors (different drugs like Viagra). Some of the others might suit you better.
As you have noticed, food interferes with Viagra. It's best to take it on an empty stomach. The same is true of Levitra. Cialis lasts longer and is less affected by food. There is also a new drug called "Staxin" that is similar to Levitra but avoids the food problem because you don't swallow it. It dissolves on your tongue and is absorbed through your mouth directly into your blood stream.
Since you had your RP at Sloan Kettering you may have heard of Dr Mulhall who is their sexual medicine guy there. He has a couple of videos on YouTube from a lecture he did several years ago. Here they are:
youtu.be/OQlGVT7HiF8 part 1 18:33
youtu.be/o7GmTZITJ5s part 2 15:20
youtu.be/ie8NkOu2VNA part 3 31:20
He talks about
food effect about
11 minutes into the third part. You might find part three worth watching.