> while he accuses others of supporting cartesian dualism when they think the brain and the mind can be separated, that you can "run" the mind on a different substrate

His views are perfectly consistent with non-dualism and if you think his views are muddy, that doesn't mean they are (they are definitively not muddy, per a large consensus). For the record, I am a substance dualist, and his arguments against dualism are pretty interesting, precisely because he argues that you can build something that functions in a different way than symbol manipulation while still doing something that looks like symbol manipulation (but also has this special property called consciousness, kind of like our brains).

Is this true? I don't know (I, of course, would argue "no"), but it does seem at least somewhat plausible and there's no obvious counter-argument.

I don't see how his views can be made sense of without dualism. He believed very much in this concept of qualia as some special property, and in the logical coherence of the concept of p-zombies, beings that would exactly like a conscious being but without having qualia. This simply makes no sense unless you believe that consciousness is a non-physical property, one that the physical world acts upon but which can't itself act back upon it (as otherwise, there would obviously have to be some kind of meaningful physical difference between the being that possesses it and the being that doesn't).