I want to stop a unit from running, I only want the unit to walk. Is that possible?

Would giving him the same running speed as walking speed and assigning the walking animations to the running animations work?

If you're using some sort of analog controller such as a gamepad or mouse, yes. If it's a keyboard, no. "Walking" in SWBF1/2 is really just slowing down the run animation and moving slower.

Ah, so I couldn't make Darth Vader walk.