The magnetic poles are completely separate from the geographic poles.
The magnetic poles are constantly moving around. The magnetic north is currently quite close to the north pole and is moving towards Siberia. In recorded history it has been as far south as northern Canada. See this link for a record of locations. On average it drifts 40 km per year.
Over many millennia, the magnetic poles sometimes wander so far that the field reverses in a geomagnetic reversal. Then the north magnetic pole becomes south and vice versa. The last one happened 780,000 years ago. In the last 83 million years there have been 183 reversals, i.e. one every 450,000 years. 188
So we can probably expect another in the next 100,000 years or so.
The earth's spin axis moves as well, independently from the magnetic field. According to NASA it has drifted about 10 m in the 20th century, or about 4,000 times less than the magnetic north. It is caused by the melting of ice in a global warming episode, by earthquakes and, on a much slower scale, by continental drift. Continental drift is caused by the rise and fall of molten rock inside the earth, and is completely unaffected by magnetic pole drift or reversal.
As for the origin of the Sahara, it started a couple of million years ago, at a time when the continents were already close to their current positions. According to one theory, it is thought that it started to form when the monsoon started to weaken as a result of the ice ages.
While the present global warming may cause it to grow larger and drier, that has nothing to do with pole shift - either magnetic or geographic.
As for the difference in sea level at the equator, compared to the poles, I suspect you are thinking about the fact that the earth is an oblate (flattened) sphere so at the poles you are closer to the centre than at the equator (by about 11 km). However, that does not affect the level of the ocean compared to the land. At the poles, both sea and land are 11 km closer to the centre. Finally, Africa has not been substantially closer to either pole for hundreds of millions of years. If anything, it is probably further north now than it was 150 million years ago. 188