ATR pledge is legally binding...and hollow, 4a gov. with no revenue AT ALL can't enforce the peaceable transfer of power
(part 3) would not- could not- be enacted, voted upon, or even proposed because that would be in violation of the pledge.
(part 2) once all tax rates reach zero, a flat tax (as is commonly proposed in place of income, estate and other taxes by libertarians)
(part one), lovingly, "One problem the pledge cannot fix becomes apparent the longer one considers the impact and the goal: