The doctrine of transubstantiation states that Christ is truly present in the Eucharist. It isn't a mere symbol. In substance the bread and wine cease to exist and become God incarnate. The accidents (the perceptible physical attributes) of the bread and wine remain as bread and wine. When you take Catholic communion you are consuming bread and wine as perceived in the physical attributes. But in the substance or essence, Christ is truly present just as much as He was during His time on Earth.
The ceremonial laid out in Mosaic Law existed only to prefigure Christ. Since Christ has now come, all prefigurement of Him is redundant. All sacrifice is redundant because the ultimate, infinitely meritorious sacrifice has been rendered and paid. It is actually a grave sin to observe the ceremonial of the Mosaic Law because such observance is tantamount to a ritual denial of Christ as messiah. Either Christ was who He claimed to be or He was not. You can't have it both ways.
The moral of the Mosaic Law as summed up in the Decalogue still applies. The moral law is eternal and universal. Adultery will forever be forbidden. But the ceremonial religion in which Christ's coming was prefigured was not. Circumcision, unclean foods, animal sacrifice at the temple, laws dictating clothing etc. That's all gone. The New Testament is clear about this.
The Gospel says that Jesus is the eternal divine Word, one with the Father. And the Word was God and was made flesh. Jesus is fully God identical with the Father in essence, but not in person.
Look, not to be disrespectful myself, but if the divinity of Christ is a controversial question for you then you're not a Christian in my books. If you don't think Christ is God and freed us from the observances of Mosaic law then convert to Judaism.
Well (respectfully) I'm certainly not Catholic.