Yes, I think you're right when you say:
Don't forget the extra goats left over from the lack of Temple rituals surrounding Yom Kippur! The High Priest would actually use a goat (scapegoat) for the atonement of sins,
Is there a Christian holiday that replaces Yom Kippur?
Not really. ...but there really is not a functional equivalent in the Orthodox Church that I can tell. I think that our Pascha has probably combined the elements of Yom Kippur and Passover.
, because in Christianity, like the sacrifice on the day of atonement, Christ's sacrifice cleansed our sins.Pensateomnia
drew the parallel accurately: "The High Priest would actually use a goat (scapegoat) for the atonement of sins, which, as the Epistle to Hebrews tells us, has been fulfilled by our High Priest, Christ."
Also, it sounds like you are right when you say: "If one were looking for a parallel, the closest that I could tell would be Great Lent, possibly the Holy Week in particular",
because lent is a period of religious humility like the Day of Atonement.
It's funny when you write: "Some of the Protestant nut jobs celebrate "a day of atonement".
, although I think they aren't really all nuts, just that they don't seem to value the Christian traditions and understanding. Since Christ played such a role as a sacrificial lamb as a sacrifice for sins that St Paul in Hebrews connects to the lamb in Isaiah 53, it appears that the Day of Atonement as a separate day of animal sacrifice for sin is superseded by Pascha. So it seems that in Christianity they should simply celebrate Paskha instead of a separate Day of Atonement, and that their problem is that they don't understand about the Day of Atonement being superseded.
But then again, this is just my opinion.Regards.