Yes, your husband has a problem but have you *really* done all you can do as far as consequences go? IMO you have not.
You don't want to divide the bank accounts because it will be a nightmare. You have not called him and told him his things are packed and he is to get them by <insert date here>. You become fearful when he prods you to get involved with the legal proceedings for divorce. And you are protecting him so in essence you are also enabling this issue he has.
IMO you should say: H, I am going to file for divorce and no, we will not be working together on the divorce. I no longer will be a part of your addiction. I have divided the bank accounts and you will need to pick up your personal items from MY home by <insert date here>
You don't need an interventionist to do any of those things. This has been a problem for now four years (that you are aware of) as per your signature. Clearly he has no desire to change or something would have happened in therapy by now. You can't change him but you can change YOUR circumstances.
