I do think some things just are what they are. And trying to make them otherwise can be just a frustrating lost cause. I know it seems like everything one reads & hears talks about how important it is to be thin. And that's fine if one can be. But I think there's something to be said for peace of mind too. And since you've tried so many different things without success, perhaps it's just best to let things be as they are.
I do recall reading an article in our local newspaper some time ago that said, for older people, carrying a bit of extra weight can actually be beneficial. The writer was a physician. And he said his experience had been that his older patients who were carrying a bit of extra weight seemed to do better than those who were thin when they became ill. I don't know it it's true. But, perhaps thinness isn't necessarily the "end-all be-all" the so-called health advocates would have us believe? I don't know. But perhaps it's something to consider...