1) Buddhism is much more tolerant of doctrinal differences than most Western religions, and it doesn't surprise me that the concept of Sunyata has many different interpretations! I would describe the insight your Zen teacher gave as an example of tathata, "suchness," rather than sunyata -- but I'm not a Zen master, of course.

2) See my comment above. No, that version of sunyata (or, as I'd say, tathata) won't protect you, which is why I recommended meditating on the other.