Clearly it is said by the priest and the CCC that the church IS sacrificing Jesus.
There is no other purpose for an altar anyway.
FWIW, Jesus did not hold the Last Supper at an altar, but at a table. And He died on a cross, not an altar.
http://www.vatican.va/archive/ENG0015/__P40.HTM
1350 The presentation of the offerings (the Offertory). Then, sometimes in procession, the bread and wine are brought to the altar; they will be offered by the priest in the name of Christ in the Eucharistic sacrifice in which they will become his body and blood. It is the very action of Christ at the Last Supper - "taking the bread and a cup." "The Church alone offers this pure oblation to the Creator, when she offers what comes forth from his creation with thanksgiving."175 The presentation of the offerings at the altar takes up the gesture of Melchizedek and commits the Creator's gifts into the hands of Christ who, in his sacrifice, brings to perfection all human attempts to offer sacrifices.
1367 The sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice: "The victim is one and the same: the same now offers through the ministry of priests, who then offered himself on the cross; only the manner of offering is different." "In this divine sacrifice which is celebrated in the Mass, the same Christ who offered himself once in a bloody manner on the altar of the cross is contained and is offered in an unbloody manner."188
Jesus is now seated at the right hand of God the father in heaven. He is not still being sacrificed.
It's not the being sacrificed that saves and obtains forgiveness, it's the death, the shedding of blood, that accomplishes that.
Without the shedding of blood, there is no forgiveness of sins. Once there is forgiveness, there is no longer any need for sacrifice.
I think that this is where we as Catholics differ with Protestants. My understanding is that we are not sacrificing Jesus at Mass. We are participating in the sacrifice that occurred on Calvary which is an on-going event. For example, Paul says that the bread we break is a "participation" in the body and blood of Christ. From my perspective this continuing apsect allows us now to "plug in" to the sacrifice through the Mass. I think you can read the passages you quote in this context.
Further, in Revelations 5:6, John sees " the Lion of the tribe of Judah" which turns out to be "a Lamb that seems to have been slain." This Lamb is recognized by most people to be Jesus. He is slain yet he is alive. I submit that this shows the continuing nature of his sacrifice. Jesus is alive in Heaven yet he appears as if he has been slain.
You will no doubt argue now that "Christ died once and for all" but I did not say he is dying again. This is the same death/sacrifice the significance of which carries through to this day.