I don't recall him ever saying anything about talking to Bullitt County, KY. He said he contacted the FBI and Greene County, VA, and both times it went nowhere. Of course - the FBI isn't going to bother with a relatively small case where the damages are only $6,000, and as you said, a county in Virginia doesn't have jurisdiction over a perpetrator in Kentucky.
He's nothing if not consistent! I have seen the screenshot of that conversation, maybe even earlier in this thread. He probably didn't like the fact that you pointed up something he hadn't done or thought of first. He really is that petty.
So at the very least, Null was involved as far as virtue signalling to make it seem like he was doing a good turn for Chris by helping the other Guard Dogs to get the Idea Guys out. I wouldn't be surprised, though, if Null knew the identity of at least Joshua Wise long before those dox dropped in January 2018. By the time Stephen Boyd got doxxed, Null was already in a very comfortable position with Chris, and it was all by virtue of being in the right place at the right time. Well... at least on an on-again/off-again basis until Chris did the thing a few weeks ago.