Imo the problem in this discussion is that you avoiding the clear biblical Truth that Peter was kept in his faith by the Lord Jesus alone.
Because this is not the case. Jesus chooses to use others to build us up in faith. Jesus chose to build a Church, and create a Body, and make us members one of another, so that we could all build one another up in faith. Peter is not alone, but stands together with all the Apostles and Prophets from whom the foundation of the Church is formed.
Eph 4:15-16
we are to grow up in every way into him who is the head, into Christ, 16 from whom the whole body, joined and knit together by every joint with which it is supplied, when each part is working properly, makes bodily growth and upbuilds itself in love.
It is Christ who has knit us together. that is why this "jesus alone’ theology is flawed.
Of course it is only God’s grace that does this, but He chooses to do it between us, with us, and through us - humans -fallible people.
Also you are avoiding the issue of the fact that just as the Lord Jesus kept Peter in the faith so He keeps all who are His.
The bottom line with this issue is whether one believes that the Lord Jesus is able to keep those who are His. I definitely don’t believe that Christians keep themselves in their God given faith, they are totally dependent upon Christ, He keeps them in the faith.
God is able to keep us, but we are also able to spurn his grace.
12 Take care, brethren, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God."
Heb 3:12
Whose responsibility is it to build up faith?
“Therefore encourage one another and build one another up, just as you are doing.” 1 Thess 5:10-11
" For this very reason
make every effort to supplement your faith with virtue, and virtue with knowledge, 6 and knowledge with self-control, and self-control with steadfastness, and steadfastness with godliness, 7 and godliness with brotherly affection, and brotherly affection with love. 8 For if these things are yours and abound, they keep you from being ineffective or unfruitful in the knowledge of our Lord Jesus Christ. 9 For whoever lacks these things is blind and shortsighted and has forgotten that he was cleansed from his old sins. 10 Therefore, brethren, be the more zealous to confirm your call and election, for if you do this you will never fall; 11 so there will be richly provided for you an entrance into the eternal kingdom of our Lord and Savior Jesus Christ." 2 Peter 1:4-11
Who is to make the effort?
What makes us fruitful and effective in the knowledge of the Lord?
Who is to confirm their call, and why?
When Jesus hung on the cross, He said “it is finished”. His work was completed. Ours is not.