Sensory stuff like misophonia is common in ADHD, yeah. I deal with it. I don't know what to offer RE: sleep because your bases are pretty well covered as far as circumstances will allow.

TL;DR, People naturally have a split attention, with the majority going towards what we're deliberately turning our focus to, and the rest going to idly surveying the environment. With ADHD, we can't really filter out useless information like someone else's noise. Things that eat up the rest of that attention are really helpful--that's probably why white noise is useful for you. I've found that steady, predictable stimming/fidgeting or putting on my own rhythmic music helps me cope with external stimulus I can't control. If I know what to expect, it's easier to ignore.