Christ’s sacrifice on the Cross is the one and only propitiation for the sins of the whole world for all time. In the Eucharist (Mass, Divine Liturgy, Lord’s Supper), the sacrifice on the Cross is not done again. Rather, the one sacrifice at Calvary is made present for the Faithful so that they may also partake in it. “Do this in remembrance of Me” may be understod as “Do this to make Me present again”.
Yup.