2) Why do you need to go back and change past U-3's?
When they changed the CPI calculation process over the years, they did not go back and change previous years/decades CPI levels (to my knowledge).
Besides, it ain't hard to change the previous numbers if you did decide to do so. You just take those that I think should be included (as I mentioned above) and add that number to both the work force and the unemployed numbers and redo the calculation. It would take all of 45 seconds per year. Big deal.