finally know precisely what the "ớt" in "tương ớt Sriracha" means...
It's about what I expected.
Chili pepper (usually the little red ones)... I've never seen chili, the beef stew thing, in Vietnam, so I would assume they just call that "chili"
Nope. "Ớt" refers to the peppers whose degree of spiciness is measured via the Scoville scale. You're talking about the dish (I assume), and so far as I know, there isn't a Vietnamese word for that, but someone living in Vietnam now would need to confirm current usage.