Hi, I know nowt about Wolf drills Im afraid but if your saying that there is a threaded shaft sticking up out of the gear with the key that youve uncovered by removeing the nut,, have you tried giving this shaft a few solid taps useing a brass drift so as not to damage the threads? I cannot see any shaft in the photo so forgive me if Ive got the wrong end of the stick. As to bronze bushes, if you do replace them it often helps if you either dip or at least pour very hot water over the alloy caseing, somtimes the the bushes will then just slip in, saves walloping them and having to tidy things up afterwards.
Good luck.