Since you seem to have exhausted the possibility of physical ailments, maybe try hypnosis? Somehow you need to convince your body that it needs to void more of these liquids during the day, rather than at night, right? Maybe the route to doing that is through the brain.
Crazy idea, I know. But having actually witnessed somebody hypnotized, I've never been able to forget how powerful it seemed. Only throwing this out there because you seem to be giving up, so I figured what the hell. Looks like somebody did a study about the effect on overactive bladders. They do mention nocturia as one of the problems addressed through a combination of hypnotherapy and behavioral therapy.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4575591/