You're forgetting how men come to faith. It is by the predestining, supernatural work of God, and not men.
Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) And hath raised us up together, and made us sit together in heavenly places in Christ Jesus" -- Ephesians 2:4-6 "But God, who is rich in mercy, for his great love wherewith he loved us,
Quickened us, regenerated us, rebirthed us with Christ while we were still dead in sins.
Not after we believed.
We have faith because first we have been regenerated by the Holy Spirit to know the things of God, to repent, to obey, to believe.
As the RCC catechism correctly notes, "Faith is a gift of God."
There is nothing in-between provided for in the Bible
Read Paul. He understands that the flesh is weak while the spirit is willing.
And so we persevere, "confident that he which hath begun a good work in (us) will perform it until the day of Jesus Christ" (Phil. 1:6.)
You talk a lot about Christians not being "perfect" and that seems to unsettle you. Maybe your problem with Christianity stems from the fact that Eastern Orthodoxy teaches that perfection is actually possible in this life, although it is actually a futile, empty and ultimately frustrating pursuit of ego and not grace.
Christ and Christianity are a lot more sympathetic to the human condition than that. God loves us so much that "while we were yet sinners, Christ died for us" (Romans 5:8.)
We do our best, knowing that we have been forgiven our sins and that at our death, Christ, not Mary, not saints, not our own good deeds, but Christ alone will bring us to God the Father covered in His perfection, His obedience, His righteousness, His salvation.
That's what "substitutionary atonement" means.
Even as David also describeth the blessedness of the man, unto whom God imputeth righteousness without works, Saying, Blessed are they whose iniquities are forgiven, and whose sins are covered. Blessed is the man to whom the Lord will not impute sin." -- Romans 4:5-8 "But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.
Who is "we"?
Paul's mission was to spread and teach the revealed Word, not to reveal. If you cannot state your belief exclusively from the Synoptic Gospels your interpretation of Paul is incorrect. If you can find where Paul is reinforcing or clarifying the Word as revealed in the Synoptic Gospels you have it right.