The Scriptures never say that one who has gained forgiveness for his sins can himself never leave God. None of those references say that. 

From Hebrews 6:
"For it is impossible to restore again to repentance those who have once been enlightened, who have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the goodness of the word of God and the powers of the age to come, if they then commit apostasy, since they crucify the Son of God on their own account and hold him up to contempt."

The very idea of apostacy in the ideology of eternal security must mean the apostate never believed, never truly became partakers of the Holy Spirit, but the inspired author of Hebrews says precisely the opposite without saying that they never truly believed. Some who do become partakers may reject and apostatize.

The verse you shared that comes closest is Romans 8:38-39. Although it sounds absolute to include the potential apostate himself, it doesn't. These are external things. It does not say "or height, nor depth, [nor we,] nor anything else in all creation." It would be tantamount to the addition of the word "alone" in Romans 3:28.

To receive is a choice, and to reject likewise. Otherwise, there is no such thing as sin.