2. Yes, both are acceptable, but the "by" form is more common.
3. I agree with the key in all cases. "Off" and "from" can have similar meanings, but their uses are different.
One can't say I live "from Broadway" with out a specified distance. By the same token, the distances mentioned in the other two call for "from". The only exception I know is with coastlines. There, one can be 3 miles off shore or from shore.
Student or Learner