But then when scientist say "there is 99% chance that asteroid will hit", the other characters says "so there is some wiggle room, lets call it 60% and move on".

Some people need to understand science is never exact. Like you are saying, they should understand it isn't exact.

Then others are like, since it isn't exact, then it isn't real.

I've heard arguments that since Climate Models have some range of error, then it isn't real, "see, there is some uncertainty". Climate change isn't real, because the models have some error. So for these people you need to be more forcefully confident in the predictions since they can't handle the nuance in discussing error ranges.