I am struggling to follow the logical progression in thought here. He starts by talking about a POI who he won't categorize, but could be. Stops to discuss current boyfriend. Then continues on about the POI again.
I agree that the description sounds like he is implicating ZH. We know ZH has talked to police, but it sounded far less formal and more like he was establishing what he was legally permitted to do to conduct his own search for AJ.
But then I start wondering because of the tangent if instead he is thinking of a former boyfriend. A boyfriend maybe the family didn't like, unlike current boyfriend which they do like? Otherwise, I can't understand how the thought progression in this statement works.
I think the step dad could be suggesting her loyal friend is a stalker, could have been so into her he would kill her, then make himself part of the investigation, who also happened to have kept a jacket of her's in his closet, and that LE was tipped off to it by somebody other than the step-dad. His only victory is having a POI other than himself, so it seems to me any focus in any other direction would work for him, thus the word salad, for the Dad who said he usually stares, doesn't say much.