Thanks everyone for your comments, I really appreciate it. I have decided to start making plans to move out. I would say that I'm calling his bluff, except that I don't think he's bluffing (even though he's peddling all the same stock-standard I-can't-do-this-we'd-be-better-off-without-each-other phrases that I've heard reported by dozens of other supporters here).
I am planning to tell him that I am open to discussions about "us" right up until I move out. After I move out, we are done - I will no longer be in his life. This is not an empty threat, and I'm not saying it in an attempt to get him to change his mind. I just honestly think it will be too painful to keep him in my life after I move out - I will have to cut contact with him altogether. But it's only fair that he knows that before I move out - if there's any doubt in his mind, he will need to speak up before I leave.
The other reason why I want to do it this way is because I suspect that what he wants most right now is to have his house to himself again ie. get me to move out and then suggest that we start dating again. This is not acceptable to me - it's commitment or bust, and I want to make it clear that it won't be an option for him after the fact. I plan to take my time moving out though - it will take a few weeks to get my sh*t sorted anyway.