To a degree this is sensible, if someone is tailgating you and you need to perform an emergency stop there's more likely to be a collision, so you need to increase the space in front of you for more gradual braking.
Same. I start driving at a speed that is safe for the distance they're keeping (in stead of what should be the other way around). That is usually quite effective.
That distance is also a function of their speed though.
You'll just have to lower it more if they start getting closer again. Eventually they'll get the courage to pass instead of hugging your rear bumper, and at safer speeds too
But it doesn't really matter; you just add a buffer in front of you that allows you to slow more gently so they don't rearend you.