You argue for a temporary and brief forsaking, but there is a counterargument for a kind of permanent abandonment.
How can Jesus, by a "mere" six hours of excruciation followed by physical death, adequately atone for my sins and yours, to stand in for our eternity in hell that we justly deserve? The answer may be, in some tens of billions of extra dimensions that God has complete freedom to create, that Jesus voluntarily is still on that cross for all eternity--indeed, a separate "version" of Him for each one of us."
I've never heard of a permanent abandonment. Where did you hear such a thing? Rather, scripture shows Jesus on the cross for six hours, 9 am to 3 pm. The sun was darkened at noon, and just before 3 pm Jesus cried, 'My God, My God ...'.
There's actually no revelation Jesus was abandoned at all. That is speculation. Rather, in John 17, Jesus says He and His Father are one. I suspect Jesus did not feel God on the cross, just as we don't always feel God, but I think God felt all His pain.
Regarding the sufficiency of His sacrifice, how six hours on the cross (and the scourging--which was almost enough to kill Him) was sufficient for the sins of all mankind, consider that God is infinite. His death in Christ pays for infinite sins. Indeed, I feel God overpaid for the salvation of mankind, even if we grow to Googleplex in number across the universe.
Ultimately, the scourging finally did kill Him, through blood loss leading to cardiac arrest. Crucifixion is known colloquially as "the moving death," because to breathe the sufferer must constantly lift himself to draw a breath; that prevented Jesus' back wounds from coagulating over those six hours. For perhaps the definitive study of the physiologic trauma inherent in Jesus' crucifixion, see this 14-page article by engineer and physician Dr, Alex Metherell, which makes that argument persuasively. It is compelling reading.
Where did you hear such a thing?
Dr. Hugh Ross has advanced this theory several times verbally, although I don't recall if his voluminous writings include it. I'll make a cursory search today on his Reasons to Believe website.
God is infinite. His death in Christ pays for infinite sins.
That Jesus' death was sufficient is settled. How Jesus' death was sufficient is (a) subsidiary and (b) speculative. I suspect we'll learn "how" eventually, but I know we will celebrate its fact eternally.