I think the way you've pieced it together so far seems to work the way I've played and envisioned it lo these many years. Some modifiers, which you've probably thought of already: While he can selectively suppress it for short times or for entire categories (like clothing), he cannot ever actually shut it off. Suppression stays even when he's asleep, if it's a simple enough category (clothes, bed).
-- Bob
---------
Then the horns kicked in...
...and my shoes began to squeak.
-- Bob
---------
Then the horns kicked in...
...and my shoes began to squeak.