Several questions... I need your help

Here are 3 questions I've got:

1. What does "to pass back the midterm exams" mean?

2. What does "to run errands" mean? It appears in a sentence that goes like "Sam needs to run errands during lunch".

3. Another one:
WOMAN: Sorry you had to miss the seminar;how're you doing now?
MAN: I took it easy last week-it's amazing what a little rest can do.
It seems that the man just relaxed at home instead of going to school, but it also sounds like that he had very little time to relax, to have a rest, since he said it was amazing what a little rest could do.Then I am confused and wonder if he spent plenty of his time on relaxation. What on earth does the man mean?


Thanks in advance.