I can't say melatonin does anything to relieve my pain - magnesium helps me here - but it certainly is the only supplement i've found thus far that i can (kind of) rely on. I have chronic insomnia which has eased up with the diet and EE etc.. but still i think i've got about 6 months to go before i can say i'm clear of any inflammation, which i think is part of the issue.
I started with 3mg last year and have stuck with the Natrol 5mg time release - can't say if the TR helps any, probably does. And i didn't think it would really work but once i ran out i realised that actually, even if it's just that it helps me wake up in the morning, and it really does. it's a necessity for me. I'm a night owl so i think it's probably helping reset my system, as you say Immersion, and for me after a lifetime of atrocious sleeping habits, i understand It's been used for years by fly attendants for that reason, I think the other trick was to skip the meal and eat again at 'a set meal time' because apparently the gut can reset your circadian rhythm more effectively than anything else.
One last thing: this idea that melatonin can do something to your dreaming; almost as soon as i started taking it i began to have vivid erotic dreams! I was transitioning on Keto and waking up every 2 hours (urinate) as well as dealing with these dreams. I'm fairly sure they happened across the board - ie. in a lucid state but also in REM (but i can't be 100% sure). Anyway, it still can have that effect if i feel the need to take 10mg worth, or restart after running out.
I did hear a talk with Dave Asprey where he said that anything over 3mg is too much and the Paleo mom says your body will begin to stop making it (or something like). But then again, there's literature saying it helps heal the gut and is an effective antioxidant, so i don't know. But, for the time being, it's better than getting 4 hours sleep!