It is also clear from Acts 3:18-19, that Peter understood that the Messiah had to suffer for our sins to be wiped out.
Actually, you are reading that into the bible there so its far from clear. Just because the word repent appears in Peter's sermon in Acts 3:18-19, does not mean the same as what Paul meant in 1 Cor 15:1-4.
Peter is accusing the Jews of murdering Jesus. The idea of
repentance for them can be viewed from the parable of the tenants, told in all 3 synoptic gospels. (Matthew 21:33-46; Mark 12:1-12; Luke 20:9-19)
When Jesus and the 12 were preaching from Matt-John, they need to repent of rejecting God their Father in the OT, and believe in his Son is their promised King and Messiah, as foretold by their prophets. The Jewish nation had rejected and killed many of those prophets.
God had mercy on them and now decided to send his Son to them now. But as Jesus told them in the parable of the tenants, they were wicked and decided to slay the son instead, thinking they can then take control of the vineyard. The words they told Pilate was really horrific from this perspective
Matthew 27:25 Then answered all the people, and said, His blood be on us, and on our children.
When Jesus was on the cross, he asked his father to forgive them for this act, because they know not what they do, the Father agreed to Jesus request.
So when Peter urged his Jewish brothers at Pentecost to repent (Acts 2:38), they are to repent from their horrific act of murdering the Son of God, and accept him once again as the Son of God and their King, since Jesus's resurrection showed, as Peter stated, he is indeed the Messiah and the Son of God. (Acts 2:36)
But of course the Nation did not, only a remnant of them did, so God blinded the nation temporary, setting his secret plan in motion to save us Gentiles, independent of Israel.
Peter, unlike what so many believe, did not preach to the Jews that Jesus died for their sins and rose again as a sign that all their sins are forever put away, which is 1 Cor 15:1-4