Yes, he could have KJ on the turn. He could have JJ, 88, 66, or given how loose he is, he could have J8, J6 or 86 on the flop. The point is you are still ahead of both his range of hands and the range of hands that will call your bet. On the turn, he's got an equally wide range of hands that will call your bet. KJ is such a small portion of his range, don't be afraid of the boogeyman. Pot the flop, all in on the turn. In the long run against this player, you'll be winning most of these hands.