Well just fwiw after reading all this, I would say (1) since no one appointed any of us arbiter of anything other than what we do ourselves, (2) it is desirable to have a uniform yearly date as the best celebration date, and (3) that January 20 is the closest date to the "real" birthday, then:
(1) For commemoration purposes it makes sense to honor the decision of the Epicureans to celebrate on the nearest 20th (Jan 20) but that
(2) for the sake of reminding everyone of the calendar issues it would be good to keep up to date a chart such as Nate is working on so that those of us who are most "fundamentalist" will be able to observe every year how the calculation actually worked and consider the weather etc of the period as the closest approximation to what they experienced at the time of the birth of Epicurus.
That should take care of our needs and we can leave for further discussion the burning question of whether our birth sign friends would consider Epicurus to have been a Capricorn, Aquarius, or Pisces!