In the 2nd pic it appears you removed the fork and that lug slid off the axle easily.
As above. You still have the nut on the end - I assume you're aware it needs to be removed to allow the axle to pull through. Generally for removal, I loosen the pinch bolts on the brake side, then undo the nut a few turns. Loosen pinch bolts on the other side and then use a rubber mallet on the nut which pushes it through a bit. Unthread the nut some more and tap again. If everything is floating it should move across easily enough.
If the lugs are still biting you can try and spread them a bit to help. Generally not required.
Key with axles. Keep them lubricated in a heavy oil/light grease and do it frequently.