*2nd.. when removing the boss nut leave it on the thread, just flush with the top of the threads and tap it firmly with a hammer to release the splines. This couples with the WD40 and a sharp pull should release it. *
This is all good except one thing you gotta pull on the steering wheel before you hit it.
If you have a air hammer it works better just use a pointed tip and drop it into the dimple just don't keep hammering until the shaft swells.

Also be advised some steering gear boxes have a high spot in the center where the gears mesh tighter for a better road feel . this is not likely the case with these little zukes but is is possible.
If the wheel is just slightly off center it's ok to reposition but check this out and be sure you have full turning radious both ways.
Having said all this this:
The correct way to fix this is to center the steering wheel and reset the toe.when the alignment is done or redone