I remember being disappointed in that Ralph Berton book (I think it was called "Me and Bix" or maybe "Bix and Me") in that it seemed more a memoir about his family and Bix was treated like a shadowy character who ducked in and out of it. Berton came into contact with Bix through his brother Vic, a drummer and percussionist with Whiteman, when Vic was either managing or promoting the Wolverines. Once again my memory may be sketchy.
There was a lot of myth, mystery and rumor surrounding Bix and that's probably why I find his story so fascinating. I have a feeling that with all the romantic speculation the guy just simply succumbed to alcoholism. It would be nice if someone could put together an objective, definitive biography but as you say maybe the facts just aren't accessible. Whatever, the guy was a poet with his horn and he left plenty of evidence of that behind.