From my experience of having just done a full strip and re build of the rear sub frame and trailing arms including the wheel bearings.
This job is not for the faint hearted.
I gave up and got a garage to remove the drive shafts from the hubs and remove the bearings.
I rebuilt it all my self.
I made the job harder by removing the trailing arms from the car.
Back to your situation you need to remove the nut, these are tightened to 200NM so not that tight but tight enough, my suggestion would be to try and clean the nut up a lot better than it is removing all the rust with a small wire brush in a drill then try and find a socket that fits try imperial and whitworth ones (showing my age) to get a good fit try and hammer it on tight if possible then also try and jam the breaker bar or impact gun in so it can not jump off (4” by 2” wood levered against a wall of something solid) you will probably get one go at it so set it up the best you can if that fails you can try to chisel the nut free you will get 2 goes at it. You will need a good steel chisel and at least a 4lb hammer and make sure the hub is supported in a solid manner so the energy goes into turning the nut not bouncing the hub around.
If that fails you are into die grinding the nut down to weaken it to either split it or turn it to get it off.
Back to when I did mine the nut was the easy bit they came off with an impact gun, the drive shafts where seized solid. That will be your next bit but if you get the nut off you can replace the nut and drive it for repair, once the hub is off you are committed to finishing the job.