And with 2), that would work, though you'd probably want to whitelist port 53 so that you can resolve names in the first place. Sounds like it should be effective, though.
The rest is just fear mongering, I'm sorry, not sure how to phrase that more elegantly or politely. I'm not an uber smart domain expert wrt certs, but we shouldn't have to be to know that valid device MITM with certs is a normal use case. And it shouldn't be used as a boogeyman man on layman users.