I realise that somewhere in your question is a need to know where the Church obtains the authority to speak for God regarding the Sacraments.
From the Catechism of the Catholic Church
1485 “On the evening of that day, the first day of the week,” Jesus showed himself to his apostles. “He breathed on them, and said to them: 'Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained”’ (Jn 20:19, 22-23).
874 Christ is himself the source of ministry in the Church. He instituted the Church. He gave her authority and mission, orientation and goal:
In order to shepherd the People of God and to increase its numbers without cease, Christ the Lord set up in his Church a variety of offices which aim at the good of the whole body. The holders of office, who are invested with a sacred power, are, in fact, dedicated to promoting the interests of their brethren, so that all who belong to the People of God . . . may attain to salvation.
895 “The power which they exercise personally in the name of Christ, is proper, ordinary, and immediate, although its exercise is ultimately controlled by the supreme authority of the Church.” But the bishops should not be thought of as vicars of the Pope. His ordinary and immediate authority over the whole Church does not annul, but on the contrary confirms and defends that of the bishops. Their authority must be exercised in communion with the whole Church under the guidance of the Pope.
1422 “Those who approach the sacrament of Penance obtain pardon from God’s mercy for the offense committed against him, and are, at the same time, reconciled with the Church which they have wounded by their sins and which by charity, by example, and by prayer labors for their conversion.”
1441 Only God forgives sins. [Mk 2:7] Since he is the Son of God, Jesus says of himself, “The Son of man has authority on earth to forgive sins” and exercises this divine power: "Your sins are forgiven."Mk 2:5, 10; Lk 7:48.Further, by virtue of his divine authority he gives this power to men to exercise in his name. Jn 20:21-23.
1496 The spiritual effects of the sacrament of Penance are:
- reconciliation with God by which the penitent recovers grace;
- reconciliation with the Church;
- remission of the eternal punishment incurred by mortal sins;
- remission, at least in part, of temporal punishments resulting from sin;
- peace and serenity of conscience, and spiritual consolation;
- an increase of spiritual strength for the Christian battle.
1497 Individual and integral confession of grave sins followed by absolution remains the only ordinary means of reconciliation with God and with the Church.