Bearing Tolerance - Radial, Axial and Tilt angle ?

How much radial motion variation of the magnet can you tolerate, and how much do you have with the current arrangement?

shafts generally need two bearings spaced far enough apart to turn the tilting loads into two radial loads.
Then when properly guided the motion allowed by the 626 bearing would be approximately the nominal internal clearance of the 626 bearing . This ignores the fits between the 6 mm shaft and the bearing ID, and the bearing OD and whatever housing the 262 is mounted in.

What is at the upper end of the 6mm rod? A motor or something to spin the road and magnet?
Perhaps that hidden upper component has enough radial stiffness to provide additional guidance.

First start by designing a proper support. You can't achieve what you want with a single deep groove ball bearing. At a minimum you'll need a double row bearing or better, two bearings. Once the support is properly designed the deflection can be predicted using general fits and tolerances information.