Instead of putting the spanner nut back on and trying to hammer up on it, put it back on just flush with the top of the drive block.

Put the handle end of the spanner wrench on top of the spanner nut and drive block and give the other end of the spanner wrench handle a couple good wacks down, hard. This will usually free the tub from the drive block.

Other tips here:

Source: Removing the inner tub on a Kenmore Series 80