Steve, scripture hardly paints forgiveness through the Apostles as the only route to forgiveness by Christ.
Before I address your proof texting, let me preface my comments by saying that I have never said that the sacrament of Reconciliation (Confession, Penance) is the only manner in which one may be forgiven. God can forgive however and whenever and whoever he chooses to forgive. I am certain that there are people whom God has forgiven who are ignorant of Christ altogether and so cannot even call on his name. We have a merciful God who desires that none be lost and it is only He that intimately knows the hearts of all people.
What I have said is that God, through Jesus Christ, has chosen the sacrament of Reconciliation as the
ordinary means of obtaining forgiveness. He wants us to go to the Church which he established in order to have a relationship with him. And that was Jesus’ entire purpose in coming to earth; the union of God and man which had been lost as a consequence of sin. Reconciliation does just that. It reunites us with our God. We have a relationship with Christ by having a relationship with his Church. Otherwise why would he have founded a Church at all? This is a gift, not some sort of penalty we must undergo.
So we partake of the sacrament because that is the manner in which Christ has chosen to be present to us in our desire to be reunited with him. Why in the world do you imagine he would have given the Church the authority to forgive sins if he did not want his Church to exercise that authority?
And so, in addressing the verses you have provided below, lets view these in the correct context, that being that Christ said to the Apostles
“Whoever sins you forgive are forgiven them and whoever sins you retain they are retained.” And this after he breathed on them and gave them the Holy Spirit.
Matthew 6:14-16 For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins.
Yes, we must forgive others if we are to be forgiven. This doesn’t say we don’t need to confess our sins as well.
Acts 10:43 - To him give all the prophets witness, that through his name whosoever believeth in him shall receive remission of sins.
Yes, it is certainly through Christ that we are forgiven. Once again, this does not say that we do not need to confess our sins. Remember, believing is only one element. “Even the demons believe, and they shudder.”
Romans 10:13 - For whosoever shall call upon the name of the Lord shall be saved.
“Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father who is in heaven.” (MT 7:21)
That’s the problem with proof texting.
Acts 3:19 - Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord;
Yes, we must certainly repent and convert. That is part of the sacrament.
James 5:16 - Confess [your] faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much.
Amen.