What to do when on-line instructor is ignoring questions?
The first two kinds of questions should be asked in the course's public discussion area so that the answers will benefit all students.  Since you've used "all the other tools" in the course, perhaps you've done that.

I suggest a concerned phone call to the department chair.  If the professor is not present in the course at all, ask, "Is Dr. X OK?  He hasn't been in the course in several weeks."  If he's around, but ignoring you, ask, "Do you know whether I've somehow offended Dr. X?  He hasn't answered any of my questions in several weeks."

The point is to give the chair a chance to make corrections without having said anything like "ignoring me."  If it has already been several weeks, I'd suggest doing this very soon. Be as specific as possible about dates when the instructor stopped responding, how other work such as quizzes is handled, etc.