Damn liberal parole officers.

(no

smiley anymore

)
Tingalf was gone for good when I had him arrested. A couple people reported that Lt Robin left to arrest him as expected, but he remained in his spot, with the guards apparently unconcerned.
As for getting rid of him, have you tried Poison Cloud? Cast an area effect spell (that doesn't need a target) near (but not directly on) an NPC and you can do damage and kill them, without having them turn hostile and without loosing any reputation. Most or all essential NPCs are protected from dying, and can not be attacked this way.
AFAIK, there is no way in the game itself to get Tingalf locked up again.