Jazakum Allahu khayran for this beneficial reminder. I know my comment comes a little late for this year's 'Ashura, but perhaps it will be of benefit for the next one, in sha' Allah.
One small addition: the expiation mentioned in the authentic hadith refers to minor sins, while major sins require sincere repentance. Also, the Sunnah is to fast the 10th together with the 9th (or the 11th if the 9th is missed), and to increase voluntary fasting during Muharram without fasting the entire month.
May Allah accept from us all.
