Artrag is a bit of a sorcerer. The game has voices without needing an Intellivoice. With ECS enabled (-s1) they sound even better.
P.S. There's no harm in keeping Intellivoice enabled all the time. You never know what you might hear.
Correct.
The Ultimate PC Interface is a great solution for using Intellivision controllers on a computer running an emulator. http://intellivision.us/interface.php