The first thing that pops into my mind about this journal is whether or not there is anything in there that could get you into trouble? Not that I think you would have deliberately broken a law because of him or anything, but unless you're some kind of legal expert, how do you know there's not something in there that could come back to haunt you? I would at least ask an attorney to look at it first.
I may not have been around when others told you to keep a journal, but I'm not sure that a journal would be considered a legal document anyhow, unless you are planning to read it to a judge or jury in court. That might be considered heresay and inadmissable, but here again ask an attorney. But I would think that, since you told the police about the journal, that if they thought it would be helpful they would have asked for it.
And I don't think you want to hurt him at all. I think you're just sick of putting up with him. He has definitely not made things easy for you.