I'm sure this is listed somewhere I can't find it.

What happens if the probability for a dude resource does not sum to 100? What happens if its more or less than 100? How does the engine treat it? What can I expect in game using a non-100 dude?

While I haven't experimented with non 100 percentage values extensively, I have observed what happens and have seen no adverse or negative effects as a result. That being said, there must be some reason why the number turns red in Mission Computer if the percentage isn't 100%, though I know not what that reason is.

It’s simply that the engine’s behaviour when the percentages do not add to a full 100% is not defined. I have no particular reason to believe that its response will be harmful, but nor you have no guarantees that the response you see today will be consistent in all cases, or in a hypothetical future version.