Managed to put some flea dope on Leo--I sneaked up on him when he was distracted by rubbing all over me...which is why I put the flea dope on him even though he lives outside now. :)
He's doing well outside. His mind is probably more active now than when he was curled up asleep in my house all day. And I think he has a friend or two among the other ferals--cats he doesn't run away from or try to pick fights with, anyway. He still meows at the door, wanting in, but he's OK out there.