I have seen the same error (first set) with restoring quizzes though it does not seem to stop them from restoring. Did the student data come into the new quiz?
The second set of errors seem to relate to the user data. I am at a loss here short of looking at the database, trying to find the quiz in question and seeing it there is still an end date there somewhere.
What does the gradebook look like? Are grades from the quiz there and unhidden?
Could you post screenshots of the quiz settings and course page when logged in as student and as teacher?