What you keep clinging to in order to justify the false teaching you are holding onto can be likened to the difference between Judas and Peter. Peter repented and came back to the Lord because he was genuine. Judas stood in the presence of Christ, witnessed the Spirit’s work and tasted of the kingdom, yet he turned back because he was not a true believer. He “betrayed” Christ, because he was not genuine. Such is the case of those who profess Christ and then deny Him today. They profess, but do not possess to know Jesus Christ, who is Eternal Life. “Whosoever believes in Christ has eternal life and shall never die.”
While I must believe what is best warranted, and thus have an open mind on this issue, you have no compulsion over calling a teaching false which has clear substantiation. Rather than facing the issue objectively, you keep resorting to superficial exegesis in avoidance of texts that stand in your way.
It is certain that Judas was damned, but the issue is whether he was ever saved. However, the Galatians were born again, set free, and in grace, but were warned of going into Judaism, resulting in Christ becoming of no effect, of profiting them nothing, as they fell from grace.
Likewise the subject of Hebrews 10 were Christians, but were warned of willfully forsaking the faith, of drawing back into perdition, rather than being of them “who believe to the saving of the soul.” (Heb. 10:19-39)
To relegate these to being unregenerate souls is not an honest analysis of the texts. However, the only way to believe to the saving of the soul is to believe, to rely on in Christ as one’s Lord and Savior, and thus one’s life will be characterized by obedience to Him. Our work is to abide, and He will perfect that which concerns us as we do. But this faith will be tested, and Christians are exhorted to continue and warned of the consequences of departing from the faith.