What's the point of asking for advice if you aren't going to take it? I'm sorry if I seem rude, but you're simply ignoring logic for your own convenience and your fish is going to die because of it. I've cared for many bettas for many years, I'm not telling you this because I have nothing better to do than tell lies to people over the internet for my own amusement. I want to help you.
I can tell from the picture that his scales are beginning to stick out, when they should be perfectly flat without any definition. This occurs as a result of fluid buildup--this fluid builds up under the skin because the kidneys have been damaged and can no longer regulate the fluids going in and out of the fish. If you would like, you can look it up yourself. This is a condition called dropsy.
From what I can see, the fish does not have ich. If it did, I wouldn't be surprised since ich is also caused by complications due to ammonia poisoning. Ich looks like small white salt-like grains scattered all over the fish.
This happened because you won't face the facts. Think about it, what would happen if you lived in a sealed closet, and your pee was vapor instead of liquid, and someone only opened the door once a month. Oh, and imagine that the only water you were given had pee in it, too, since fish have to drink in their tank water. Your lungs would burn, and the poison would wear on your system until you were dead. It would be extremely painful, the ammonia would prick at your skin, it would burn your eyes and your nose.
The idea that my theory isn't possible because the fish has been like this for so long is pure ignorance--bettas are very resilient fish compared to other tropical species. They can take a lot of abuse, but it doesn't mean you should intentionally torture them with prolonged ammonia exposure.