the earth isn't always covered in ice, for most of the time there is no ice on the surface. all the ice melted before 3 times, the earth didn't become unbalanced.

even if all the ice melts (which it will) the water weighs the same as the ice did, so why would it cause balance problems? the weight of all the ice is tiny compared to the weight of the planet.

the magnetic pole shift happens all the time and is well documented, as magnetic compasses have been used for navigation for a long time. therefore it is necessary to know where the compass is pointing to navigate accurately. magnetic pole shift has no appreciable effect other than requiring some calculations for navigation.

physical pole shift would be catastrophic, however it has never happened, and probably never will happen due to the enormous forces that would be required to make it happen.