You say the wheel/hub won't come off the shaft, but that it moves fore and aft at the hub.
Do you mean that the shaft moves fore and aft along with the hub frozen on it?
If it is the shaft moving back and forth and the hub is frozen on the shaft, I have had repeated success in loosening the hub on the shaft by pulling the hub/shaft assembly aft, put the nut on the shaft and tapping the shaft nut with a large hammer (I always have a 32 oz hammer in my tool box). A dead blow hammer will work as well.
If the problem is different than I stated above, please let us know.