Q5. Can you see through it? Can you still see the airport? If you can see through it, it's not a cloud as far as Im concerned. As long as you still have the airport or the traffic to follow in sight, no problem.

Q6. Do nothing. A high speed abort is a hell of a lot dangerous than a rejected takeoff- especially at speeds above 80 knots. Doesn't matter how long the runway is. I rejected once at 110-115 knots on 1L at Washington Dulles... 11500'. We turned off at the end after heavy (uncomfortable) braking.

After take off, it becomes a non-issue, since you aren't required to have them on... mention it to the captain later just to make sure there's nothing wrong with his harness.