4. The speed legal maximum limit is a target all must achieve and not a limit given the prevailing circumstances
This one is a special case though. If you have a three lane motorway, it's sunny, middle of the day, with relatively low traffic, a muppet driving at 80km/h on the fast lane is nothing more than a muppet.
The speed is not a target but there's no reason for people to do less than the marked speed if there are other lanes available.
I think it should be a target. As you say, someone travelling at 80 in a 100 zone is just as much a nuisance as someone tailing you trying to do 120. If our speedos were accurate we could all do 100, no-one makes silly overtaking mistakes, no-one holds up traffic.... with the development of "Driverless" vehicles this could all be negated in the near future...but where's the fun in that
There is often occasions that traveling at 100km/h is not safe, that is why you can get ticketed doing so.
I am not saying people should ALWAYS drive at 100km/h. I am saying that people driving under the speed even if conditions allow should be good enough drivers to move over to the slow lane and let the others keep going.