just cooperate with the police so that he can get the rest of his things, and get out of your life. I think the only reason he brought a policeman with him is to assure that he would be able to get in to get his things. actually, it's good that he did that.
as far as the bills, pay them, send him a certified letter documenting what you paid, and what he owes, give him a deadline in which you'd like them paid, keep documentation on anything you send and anything that is said, and then (if it's worth it to you), sue him in your local small claims court for what he owes you.