If the axle has never been removed or hasn’t been removed frequently it isn’t unusal everything is stuck. Yes, use a rubber mallet to hammer everything off/out. Go get some emery cloth, it’ll be around the sand paper at the hardware store. Spray the axle w/ WD40 and go to town with the emery cloth to knock down the burrs from the set screws, hubs, sprocket ect. You could also get a hone for your drill to use on sprockets and hubs.

Take out the pinch bolt and tap a screw driver into the split line to spread it and it will slide off easily. Use a piece of flat wood to tap the end of the axle even if using a mallet, very easy to bend the end of an axle. The axle needs to be free of any high metal a small fine file followed by fine sand paper works then clean it good. Don’t hone a hole with a keyway.

Gif

I’ve also found that if you’re very careful, you can rethread the pinch bolts in from the back and tighten them down onto a washer slid into the groove and that levers the split open without dinging it with a screwdriver…. Be careful not to really crank down or bugger up the threads, though.