Peter never fell away from the faith, as soon as the [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] crowed he wept bitterly. He lost the courage of his convictions, stumbled, and immediately struggled to his feet. Peter would continue to struggle, even after his testing during the trial of Christ. Remember the passage where Jesus is asking Peter, 'Peter do you love me'? Peter kept answering, 'Lord you know I love you'. What you don't get from that passage is they are using two different words, Jesus is saying agape, Peter is saying philieo, divine love vs. brotherly love. Jesus was about to tell him the death he would die, I can well understand his hesitation, it reminds me of the complaints of the prophets.
This is the first time the Gentiles would hear the gospel as a group:
All the prophets testify about him that everyone who believes in him receives forgiveness of sins through his name.” While Peter was still speaking these words, the Holy Spirit came on all who heard the message. (Acts 10:43-44)
That is a singular, one time event. It is the pattern for the gospel throughout the New Testament with regards to hearing the message, believing, and being marked with the Holy Spirit of promise:
And you also were included in Christ when you heard the message of truth, the gospel of your salvation. When you believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory. (Eph. 1:13-14)
Ephesus worked, they founded the seven other churches of Asia Minor that became the largest evangelistic effort of the first century. Paul tells them early and often, it is by the hearing of faith and the indwelling of the Holy Spirit that is 'a deposit guaranteeing our inheritance'. Nothing about your performance being a condition, but based on that singular event, the manifestation of the Holy Spirit through the gifts and callings of the Holy Spirit they became fruitful ministers. You have performance out there saving you or keeping you saved and you are missing the first and most essential steps in the process of practical righteousness, the salvation that is by grace through faith.
A couple of elements here, you are enlightened and tasted the heavenly gift, being partakers of the Holy Spirit. They had experienced the gospel and the power of the Holy Spirit, what the particulars are here isn't mentioned, not that it's important really. What matters is that they have. Now they are in danger of drifting back into the legalistic snare of Judaism, warned against in Galatians as well. They had worked, they had experienced the manifestation of the Holy Spirit, they even suffered persecution. Now they are being tempted to go back and take on what Peter called a yoke neither we nor our fathers could bear. It's not like they had buried their talent, these were not wicked and lazy servants but fruitful ministers that are being tempted to embrace a works righteousness. If you go back to that after being saved by grace it's apostasy, which literally means to fall away, the idea being to fall away from the faith. You can't be saved by grace and perfected by works, it just doesn't work that way. Paul worked harder then all the other Apostles, at least according to him, by grace:
If one were to ask the Apostle Paul how it is that he worked so hard and suffered so much and bringing so many the Gospel, he would, and did, tell us that it is by grace.
But by the grace of God I am what I am, and his grace to me was not without effect. No, I worked harder than all of them, yet not I, but the grace of God that was with me. (I Cor. 15:10)
I have yet to make an argument that repentance is not a part of salvation or that works do not follow, I've said nothing of the sort. The gifts of the Holy Spirit (1 Cor. 12) that build up the church through the ministry of it's members literally means grace (charisma). All this performance based salvation, where is the grace that saves, the justifies, that sanctifies and equips the saints for service. Your clearly and obviously missing some steps and key ingredients here.
Have a nice day
Mark