I've been using a two step toggle.
0 = off
1 = on

/console AutoInteract 0
/console AutoInteract 1

I like having IWT built into the default DPS.
But when you do, you need a method to disable it.
We cannot disable the wow keybinding.
But we can easily disable the CTM, via the console command.
Or alternatively, through 'Mapped Key State Actions', choose to push or not push the IWT keybind.