You won't find hard evidence for any of these things. For Christ's sake, it's barely been studied. There are zero comprehensive binding assays covering the big receptors for the well known compounds, much less for all of the alkaloids it contains.
Take it or don't take it, stop fretting about it on the forums. Yeah, I get it, you don't want to hurt yourself with it. Good news, it's about as safe as these things get. Bad news, you're gonna have to take that on faith because the sorts of studies you need to answer your questions just don't exist.
Stop posting a million questions and do some independent research. There's nothing we can tell you that you can't figure out on your own. Forums like these are good for passing along anecdote and what we've found worked well, what we liked, etc. They're not so good at providing anxiety ridden members with answers to questions like 'what neural pathways does kratom work on?'
If you're going to insist on knowing every little detail about the potential risks, stop posting here and sending three dozen pm's and expecting us to spoon-feed you every goddamn answer, get the journals and start reading what you can. You can find most of the articles free of you ask nicely and look hard. It shouldn't take you too long to exhaust everything of value. Many of them won't have anything useful to you beyond the available abstract.
I think, perhaps, the biggest risk with kratom is consuming the more coarsly ground leaf and having that gritty stuff cause you ulcers. I think it must because it's definitely the cause of my stomach pain recently. A few days with subs again and it's greatly diminished. Consuming a lot of tums in the meantime.
I blame a combination of the kratom and opioid withdrawal that kratom wouldn't cover for the diuretic action. My mouth was also over-salivating, not drooling bad, but annoying when try it to sleep. When I'm in withdrawal, I notice these things more, in addition to the relentless RLS.