Galvanic corrosion is the enemy and penetrating oil, hammer and heat are the solution. Sometimes the corrosion is too severe and you can't save the threads. After soaking overnight again, try heat and a heavy hammer. You might get lucky. If it won't give a time sert installed by an experienced tech will save the hub. It's only money.
Here is a homemade penetrating oil that is tested and performs better than any off the shelf product at 1/10th the price:
Make a better penetrating oil